Been using the K90 for the last 6+ months. Was using the PS85 and looking for something with a little bigger sweetspot and more power. After not using the PS85 for a long time, I tried it again a couple weeks ago. Had been playing very sparingly for a couple months and was *REALLY* sucky a couple weeks ago. So I decided to use the PS85. Instant improvement. Used it once more and then yesterday. The conclusion I'm beginning to arrive at is this: I play better with the PS85. Not for every shot, but overall it's better. FH: K90 for angles. PS85 for depth and control. BH: PS85 hands down. volleys: K90 b/c it has a bigger sweetspot and also for reaction volleys. Touch goes to the PS85 and control goes to the PS85. Overheads. about a tie. 1st serve: PS85. 2nd serve: K90 dropshots: PS85. half-volley: about the same. But man I just hit my groundstrokes better w/the PS85. Not sure why. Don't shank more often either. The sucky thing is that I've sold most of my PS85's and am down to just a few + 1 st. vincent and it doesn't appear I can purchase any more at a reasonable price.