I don't really think it's a matter of there being more good players on Republic side, but more less bad ones on Republic side. There are plenty good players on Republic side, I just don't feel that (m?)any of them are much better than the Empire's good players.
Republics always seem to work together well and Focus healers, protect healers, etc etc very well, even as pugs. While Empire side...doesn't, unless it's a premade.