Well, Ive heard there isnt that much difference in power, just feel. Makes sense as mass and SW will trump stiffness and the 63ra has slightly higher SW all other things being equal. I can say the 63ra is a very different feel than a strung RA at 64... you really do notice the flex.My TC95 70RA does everything great. But I have to admit I'm considering my 2nd being the 63RA version. A softer racquet wouldn't upset me one bit. The reason I got the 70RA in the first place was for increased maneuverability and more power. I wonder though how much of a difference in those 2 factors the 2 versions are.