Khrushchev wanted to (1) test his political power, and (2) to please the Ukrainian population, and (3) to shift the rebuilding cost to the Ukrainian republic.
Khrushchev wanted to test his political power
If anyone would wanted to challenge Khrushchev, just rising to power, his controversial idea and hollow arguments would be a perfect occasion. The stake was very little at the same time. Seemingly Khrushchev wanted to test his position before more important changes he may have been planning. http://books.google.com/books?id=RwfIEhLDaMsC&lpg=PA310&pg=PA311
Khrushchev wanted to please the Ukrainian population
While the Russian and Ukrainian cadres were in great friendship ever since 1930s (1920s?), Ukrainian people's drive for independence was a recurring problem for the Soviet Union. During World War II this drive has risen again to a great extent. After the war, Soviet power went into a de-facto war with Ukrainian nationalists and relations became very strained. http://books.google.com/books?id=DHFDjhPugJIC&pg=PT199&hl=en&sa=X&ei=OlGKUMH9DISxtAauk4GwDw&ved=0CFQQ6AEwBw
The Crimea had an opinion of a crown jewel, the best vacation resort in Soviet Union. So the gesture would appear favorable to Ukrainian commoners. In reality...
Shift the rebuilding cost to the Ukrainian republic
In reality , after the 1944 mass deportations of Crimean Tatars the region became an economical disaster zone. It would require major investment, and Khrushchev wanted to shift this to the Ukrainian budget. http://books.google.com/books?id=l5uiWHgRphQC&lpg=PA500&pg=PA499