So i got to hit with the 90 and my RF97 today. RF97 hits a way heavier ball with a higher trajectory. I can hit more angles, more spins, more touch, more varied paces, more varied trajectories and just do more with the 90. The 90 is old school tennis, strategy, finesse, angles. RF97 is modern tennis, crank the ball. 90 is insanely easier to serve with than the RF97. Also easier to serve with compared to my K90 because of the lower swing weight. I think the RF wins more matches at higher levels, but at all levels at 4.5 and below, i'd think a 90 user with the skills could have great success. With the RF97 i lose some quickness and finesse, but do get more easy power, great defense and the ability to rip winners. So this week I'm sticking with the RF97. The 90 is a lot of fun though.