Hi,
There isn't a very large trend, but historically Chinese defenders have shifted to playing with short pimples rather than long pimples (Wang Xi & Hou Yingchao are good examples. as well as Wu Yang and Fan Ying on the women's side). This is because short pimples allow for a lot of variation and deception on backhand chops, and at their level they are such good players that the relative loss of control when compared with long pimples doesn't really matter to them.
Most other defenders use long pimples - all the top Korean defenders still use long pimples as it is what they prefer, and they tend to use them with slightly thicker sponge so that they can still vary the spin on the ball. At most levels, long pimples are probably better but at the top level it becomes closer to being even - though I think long pimples probably still have the edge on short pimples. Ultimately it's personal preference/what players have coached into them as youngsters, but it's unusual to see many non-Chinese high level defenders playing with short pimples. Yuto Muramatsu is the only exception I can think of off the top of my head, and he is nowhere near Joo Se Hyuk's level (who uses long pimples).
Hope this helps!