It all boils down to preference, and until you've ridden both, who's to say for you? I ride both. I prefer 700cc. But my go-to commuter currently sports 26" wheels with 1.5" slicks. Go figure. Supposedly, smaller wheels = more responsive, but harsh; larger wheels = less responsive, but more comfy. I guess a generalization could be made for smaller wheels in the city where you certainly need to be able to change direction and stop quickly, whereas if you're riding longer distances in more rural settings, 700cc makes more sense. But I'm not sure I'm riding at a level in either setting where performance makes much of a difference. Or rather, any small gain afforded in either situation by tire rim size is more than offset--by a large margin--by my lack of skillz.