Built in the early 1910s, Japan's Kongo class battlecruisers had eight 14-inch guns, a speed of about 30 knots, and a displacement of about 26,000 tons. This gave them advantages over British contemporaries such as the Orion class battleships (ten 13.5-inch guns, 21 knots and 22,000 tons displacement), but perhaps less so compared to the Revenge class battleships, which had eight 15-inch guns, 30,000 ton displacement, and 21 knots.
In the 1930s, the Kongos were upgraded to battleships by the addition of armor that increased their displacements to 32,000 tons. A source that I read rated them as being "comparable to the newer battleships of the King George V class (built during the treaty-busting rounds of the late 1930s. That seems like an exaggeration, because the King George Vs had 25% more guns (ten 14-inchers versus 8) and 30% more displacement, but were slightly slower (28 knots).
Even so, is it fair to say that the Kongo class battleships were more nearly like the King George V's built 25 years later than their peers of the Orion and Revenge classes? Put another way, how much more (or less) difficult was it to produce the superior speed of the Kongos compared to the greater heaviness of the Revenges and the King George V given the industrial technologies that were available in 1910-1915 versus 1935-1940?
My specific belief is that "speed" was harder to achieve in 1910-1915 than "heaviness," whereas "speed" was much easier to achieve by 1935. Am I right or wrong?