Most of my PCPs are now .25 caliber. I have mostly shot the JSB 25.39 grain Kings. However, I quite recently bought an FX Panthera also in .25 with which I am tuning for the JSB King Heavy and King Heavy MKII. At this point, I'm not sure which will wind up shooting the best.
I'm going to the Heavies primarily for Extreme Benchrest. Even with my limit of wind reading of +/- 1.25 mph, I found that it is not good enough to get into the finals with the lighter pellet. I could have gone with a .30, but that just adds to the expense, and would likely have to fill during a match, I'd rather not get distracted having to fill my gun while shooting.