I've never seen any side by side data on knife edging vs. not. But! I have a friend that i see every now and again who is the head tech on an AMA Superbike Team. He used to build MotoGP 250 bikes back in the 80's and 90's. We were talking 2-stroke theory and he mentioned that knife edging was the way to go; amongst the other things we talked about. In my opinion it probably only makes a tiny difference, but I trust his advice, having built up bikes to such extremes.