I played my match with the PS97 tonight, so I will post my first impressions. Mine is strung at 52 lbs with Kirschbaum Pro Line II, an identical string setup to my Ai98 so I can give them a fair comparison.
The biggest difference is in the head and string bed. The head on the PS97 feels a bit lighter and more maneuverable, however it is slightly less stable. Maybe I just didn't have a great net game today, but I found it to be slightly less solid and reliable at the net than the Ai98.
I think the enormous sweet spot is the reason that other reviewers claim that the PS97 plays softer than it really is. The Ai98 feels crisp across the entire bed with relatively little dwell time, and a direct hit on the center feels only somewhat more lively than off-center hits. It's true that impacts are muted with the Ai98 because it is relatively flexible, but there is still a noticeable impact on most of my hits. In contrast, the PS97 has a huge sweet spot where the impact is barely felt and the power is amazing. It does drop off quickly and the frame stiffness becomes apparent outside of that area, but you have to miss pretty badly to not hit that big sweet zone.
Otherwise, the two racquets swing similarly in terms of weight and feel and have about the same spin potential. I had no trouble adjusting my serve to the PS97 so I would say that they were pretty similar there, too. I didn't feel like I had my best serve going today so I can't say which ultimately is better.
To summarize, the key difference between the racquets is the huge PS97 sweet zone that feels plush and generates tremendous power. The Ai98, in contrast, feels a bit more crisp across the whole string bed and provides more feedback and stability. The maximum power levels are probably similar but access to power is easier on the PS97. I did not get the chance to try any cute touch shots with the PS97, but I suspect they are not a strong point for this frame. However, although I didn't feel confident that I had pin-point precision with the frame, I did find it very forgiving in terms of slight timing and positioning mistakes in my strokes -- probably moreso than the Ai98.
I will certainly post again and revise my assessment once I've hit a few more times with these frames back-to-back.
