Obviously the 11t is bigger but the main thing in here is how thick the wheels are. The campagnolo 10 have no play and the axle area is thicker than the shimano ones, besides the shimano ones have a lot of play and when put in a campagnolo RD (my case at least) they get even more play, as somebody mentioned, thats the reason some noname kits have an extra set of washers if the pulleys need to be installed in campagnolo Rds