I want to compare unit for unit parity, let's say at the platoon or company level.
Let's say the equivalent of a German and Soviet armored company approach each other in 1941, 1943 and 1945. Evaluating the equipment in a vacuum is not interesting. To appreciate why the Germans dominated in 1941, why they lost that dominance, and why the T-34 is considered the best tank of the war requires looking at the whole picture. Here's what I'll consider for who wins...
- Quantity of tanks they're likely to have
- Type of tank they're likely to be equipped with
- Quality of that equipment (scopes, welding, radios, etc...)
- Readiness (ie. how often they break down)
- Crew training and tactics
- Supporting units (air, artillery, infantry)
Here's the break down for summer 1941 at the opening of Operation Barbarossa. The Soviets have vast quantities of tanks, about 13,000 on the western front vs the German's 3,350 for the invasion. But the Soviet tanks are dispersed while the German tanks are concentrated allowing the Germans to gain local superiority in numbers.
Less than half of the German tanks are modern Panzer IIIs or IVs, most were the adequate Pz38 or the less adequate Panzer II or even Panzer Is. The Soviets are fielding mostly T-26 and BT-7s with a 45mm gun (quite adequate for the time) but their armor is a joke. The T-34 and KV series will wipe the floor with most German tanks, but they only exist in small numbers and are unlikely to appear at this point in the war.
In 1941, German armored tactics and training are the best in the world. There is a radio in every tank allowing fine command and control. German optics are fantastic giving them advantages in long range engagements. German planning and logistics ensure a ready supply of fuel, ammunition and intelligence.
The Soviets, in contrast, are the worst. Most crews have received little training and little instruction. Their optics are terrible, if they exist at all. Radios are reserved only for command tanks to speak with upper echelons, individual units must communicate with flags. As a result, their tactics are simple and very slow to change. Their logistics are a mess and many tanks have inadequate ammunition and fuel and often no idea where they are and where the enemy is. Maintenance is poor and breakdowns are common.
The Luftwaffe dominates the skies and can attack at will. The Soviet air force is destroyed in the first week. Unlike most other air forces, the Luftwaffe's mission is to support the army and a German ground commander can count on excellent air support. The world will see nothing like this air-to-ground coordination and dominance until the Allies roll through France in 1944.
In 1941, the Germans wipe the floor with the Soviets. A well trained, well supplied, concentrated German armored unit on the attack is likely to run into packets of confused, surprised, poorly armored T-26s and BT-7s rolling across open fields. Even if a rare T-34 or KV-1 does appear, the Germans have experience with the Allies fighting superior tanks. With their superior training, tactics and communication they can rapidly outflank and destroy it, or use their radios to call in an air strike or artillery.
Fast forward to summer 1943, the Battle of Kursk. Much has changed. The Soviets have learned, and the Germans have lost. Both have bled. The Germans have lost the initiative and Hitler hopes to regain it in one throw of the dice. The Soviets will be ready.
On the Soviet side, 12,000 T-34s poured off the production lines in 1942 and 15,000 more will come in 1943 along with thousands of SU self-propelled guns and hundreds of KV/IS tanks. All previous designs have been dropped as a waste of production, everything is focused on T-34 and KV/IS hulls. The 76mm gun is now considered the minimum with some vehicles carrying 100mm, 122mm and even 152mm guns.
German production is struggling so badly and their needs so desperate that rather than stop production to retool some factories are still producing thousands of obsolete Panzer II, 38t and III hulls. These hulls are used to make self-propelled guns like the Marder, Wespe, Grille and StuG III. Only 3,500 Panzer IVs will come off the production lines, even upgraded they struggle against the T-34. Their salvation is supposed to be the Panther and the Tiger, but only 2,000 and 700 will be produced this year with many teething problems to hamper their effectiveness.
The T-34 proved such a shock to the Germans in 1941 and was so superior there was serious consideration to simply copying it. If they had, Germany may have had the tank production to win the war. Instead they decided the upgunned Panzer IV and the excellent but very complex and expensive Panther would be the solution.
Soviet tank production is aimed in one direction, east towards Germany. In contrast the Germans are spread thin fighting the Soviets and the Allies in Italy as well as defending thousands of miles of coastline waiting for the expected Allied invasion. German tanks will be scattered all over Europe further reducing their numbers facing the Soviets.
German quality remains very high, with some slippage due to hurried production, increasing use of slave labor, and harried logistics and transport. Soviet quality has improved greatly. Radios are appearing, optics have improved. The simplicity of the T-34 means poor quality and hurried production does not translate into poor combat performance.
Due to their high losses, German crew training has plummeted. German tanks and tactics are complex and require much training to be done effectively. This is further hampered by the tendency for experienced crews to remain in the fight rather than go home to train.
Soviet training and tactics are... not entirely criminally negligent. Soviet tanks are simple to operate, and Soviet tactics are equally simple. The tendency is still to charge at the enemy and fire on the move closing the distance to negate the German advantages in gunnery and maneuver. The difference between 1941 and 1943 is the T-34 has the armor to survive this tactic, and the Soviets have learned to concentrate their armor.
German commanders have the advantage of a three-man turret (commander, loader and gunner). The commander only has to command greatly raising their situational awareness. The T-34 is hampered by it's inefficient two-man turret (commander/gunner, loader) and overworked commander.
German logistics are strained both by the scale of the war effort and their now very long supply lines. Fuel is becoming scarce, but ammunition is still plentiful. German maintenance remains excellent, but is hampered by the complexity of their designs and their numerous spare parts. While the Panzer IV is a mature design, the Panther and Tiger are as likely to be knocked out by breaking down as by enemy fire.
Soviet logistics have improved, but remain spartan by Western standards. However, short supply lines, enormous production and a limited number of designs means lavish ammunition is available. Maintenance is poor, but sufficient for the simple T-34. Intelligence and planning has improved, tank commanders will now have some idea what's in front of them.
The air is hotly contested and neither side can count on air support. The Luftwaffe has lost air superiority, but the Soviets have hardly gained it. The dearth of radios in Soviet tanks means they cannot call down close-air support. However, the IL-2 can brave conditions that would rip other aircraft to shreds and units are willing to absorb heavy casualties. In contrast, the Ju-87 Stuka is revealed for the lumbering, slow, vulnerable aircraft it always was; without air superiority it is suicidal to fly.
In 1943 our two units are likely to be composed of StuG IIIs and Panzer IVs on the German side and T-34s on the Soviet. The StuG III is an infantry assault gun pressed into service as a tank destroyer. They possess a good gun, good armor and are good at hiding. Best of all, they're cheap. The Panzer IV and T-34 are roughly equal in armor and armament. Given equal numbers, and with their superior tactics, training, radios and optics, the Germans would likely win. But there won't be equal numbers. The Soviets have 2 to 3 times the tanks and tank destroyers on the Eastern Front as the Soviets.
Even so, the Soviets took staggering losses. From what research I could find, the Soviets were losing fighting vehicles almost as fast as they could make them. However, it's not clear how much of this was due to tank-on-tank losses, breakdowns, or infantry weapons. The Germans focused much effort on developing and producing the Panzerfaust and equipping tank hunting teams.
In 1943, the German have lost air superiority, most of their technological edge, and are still fighting at a numerical disadvantage. But they retain their edge in tactics and training which proves decisive to at least fight the Soviets to a stand-still until the disaster at Kursk. The T-34 has great numbers and great potential, but it's squandered by poor training, poor tactics, and a poor turret design. The lumbering KV tank is evolving into the eventually terrifying IS tank, but is not available in sufficient numbers. Soviet high command is making great advances, but the Germans are still able to make some sweeping victories. The Germans still have the edge, but it is rapidly diminishing. They put their faith in increasingly heavy, complex and expensive tanks to save them. Their "wonder weapons" will not stem the tide.
It's February 1945. The Battle Of The Bulge has failed and with it goes the cream of the German offensive reserves. The Eastern Front is rapidly crumbling and the Soviets are only 50 miles from Berlin. There is no hope for Germany to win, but they fight on.
Amazingly, the Germans crank out nearly 20,000 AFVs during 1944. 1,700 Jagdpanzer 38s, 4,000 StuG IIIs, 1,000 StuG IVs, 1,700 Jagdpanzer IVs, 3,000 Panzer IVs, 4,000 Panthers and 1,000 Tigers. The supply complexity is further hampered by continuing to produce six hulls.
The Soviets have put out 28,000 AFVs in 1944. They continue their two hull policy, everything is derived from the T-34 or KV/IS. This simplifies production and logistics. 7,000 SU-76s (now barely adequate), 3,500 T-34s, 10,500 T-34/85s, 2,300 SU-85, 100 and 122s, 2,200 IS-2s, and 2,500 ISU-122s.
As before, the near match in numbers does not work out for the Germans. They are now fighting on three fronts (Italy, France and Soviet) and have made some very poor choices about how to allocate their armor. Many heavy tanks, sorely needed in the East, are sent against thin American armor in the West and Italy only to be destroyed by Allied air power. The Soviets field over 12,000 fighting vehicles while the Germans can likely scrape together less than 3,000 on the Eastern front.
The Panther is now being produced in number, and many of the teething problems are solved. Its armor and mobility is excellent, and the 75mm/L70 gun easily penetrate the front armor of a T-34 at range. However, the Tiger will always remain a heavy, fuel hungry, temperamental, expensive waste of resources. The majority of German armor is now cheaper self-propelled guns.
The T-34/85 fixes many of the problems with the T-34, but it remains an early war design. Its 85mm gun could see off most German vehicles, but it struggled against the front armor of a Panther or Tiger. The new turret finally gave it a 3-man crew with more room (by Soviet standards) and allowing the commander to command. Despite some effort to improve the armor, it was now inadequate. This was made up for by numbers, but also the availability of the IS-2 heavy tank and many heavily armored SU tank destroyers.
German training and tactics continued to plummet, Soviet continued to improve. Both sides had to replace staggering loses, but the loss in experience and training would hurt the Germans far more. The Germans had always relied on superior tactics to win battles, while the Soviets did not. The Soviets were making less mistakes, and the Germans were making more. Hitler was interfering more and more, while Stalin and his political officers were interfering less.
Soviet tanks were never particularly reliable, and now they had traveled long distances putting wear on their equipment and were fighting with extended supply lines. Still, the Soviets kept their units supplied. In contrast, the German supply lines were now very short. However, their logistics system was shattered by Allied bombing. Much of what was produced in Germany never reached the front. Fuel was scarce and mobility limited making it difficult for the Germans to concentrate their armor, conduct an offensive or a mobile defense.
The skies were dominated by the Soviets, and the Soviet artillery support was lavish. In a set piece battle with plenty of time to plan, or roving across the countryside in search of targets, it was devastating. Tactically it was still hampered by poor communications.
In 1945 a Soviet unit is equally likely to be equipped with T-34/85s, SU/76s or a more capable tank destroyer. The Germans will likely have tank destroyers. If they do have tanks they will be Panzer IVs or Panthers. The Soviets are on the attack, have superior numbers and have learned to concentrate their forces. The Germans are on the defense, have inferior numbers, are spread thin and no longer have the fuel to concentrate. Our hypothetical battle will likely be a large number of Soviet T-34/85s with a few SU-122s advancing and encountering individual or pairs of German self-propelled guns, well-hidden, at an important bottleneck with good sighting. The Germans will likely get a few kills before being overrun by T-34/85s, knocked out by a massive 122m shell, or smothered by artillery.
At what point did Soviet armored units have qualitative parity with the Germans? Quality is usually taken to mean which is better given equal numbers. Given this definition of quality, I would say they never did. But warfare isn't that simple. Everything is interlocked. So much happens before the battle to determine the outcome. And quantity has a quality all its own.
In 1942 the T-34, with German training, tactics, radios and optics, would have been devastating... but that was impossible with the trade offs the Soviets made. In 1944, the Panther produced in the same numbers as the T-34 may have turned the tide of the war... but that was impossible with the trade offs the Germans made.
From this holistic point of view, Soviet armored units achieved superiority over the Germans at the Battle of Kursk. The Soviets derived the German plan, prepared a trap, kept it hidden and halted a major German offensive before a breakthrough while taking acceptable casualties. The Soviets had stood toe-to-toe against everything the Germans could throw at them. The Germans never regained the initiative on the Western Front. By the time of the D-Day landings, the Soviets had already won the war, the western Allies just sped it up.
Sources, in addition to the usual Wikipedia sources for specific vehicles and battles...