The only things that I can come up with are:
1) Less paddles = less weight for the motor to turn, but somehow, I dont think so.
2) Less paddles could *theoretically* mean that there is a solid queue of balls waiting to be pushed into the feed neck instead of 1 ball then a gap ( for the paddle arm ) then the next ball etc.. However that would have to mean that the paintballs would have to be constantly perfectly arranged and drop perfectly into the gap created when the balls have been fed.... all in all a bit dubious on that since if it worked im sure the manufacturers would have picked up on this...
My 2p - which is prob about to get flamed..