You don't judge a stroke by power alone, but by its effectiveness. Think of how many times (millions) we've seen Fed in an impossible position at the end of a long rally, the other guy is at the net. And then Fed hits one of his patented bh passing shots, or gets it back right the the feet with impossible accuracy and spin. That shot has saved countless bp's. I guarantee you, no other player in history would be able to hit clutch backhands with that much variety. For ~5 years, every single player went after Fed's backhand, and with the exception of Nadal, no one was able to make an impression.