Component (3 video cables w/RCA): 25% better than composite
This was for a reference, 50" RPTV. A smaller display shows LESS improvement, a larger display shows MORE.
So how big is your display?
Note: If you have a HD TV that tries to take the signal and turn it into progressive, you really, really, really want to use Component cables. Because of all the things the TV is going to do with that signal, that little 5% improvement from SVideo->Component might make a visible improvement for a HD TV.