On your Racquet Help page you note that a heavier racquet = more power and that a stiffer frame = more power. But as I was comparing two racquets of interest, the Head Youtek IG Extreme OS (10.5 oz. and 70 stiffness) and the Babolat Overdrive 105 (9.8 oz and 68 stiffness) you note that the Head has medium power and the Babolat has medium high power. This would seem not to mesh with your stated criteria. So there must be some other factors involved. What are they? Thanks.