Well, it really depends on what kind of shows they are. If they are smaller open shows, then, normally, the horse that is well fit, well conformed, and well turned out will beat out the beef cattle horses any day. It is usually the breed shows with the AQHA and APHA where you see those nasty, peg-legged, Schwarzenegger looking horses.
That being said, your best bet would be the bay (with some proper work to muscle him up a bit in all the right places) or the paint. They seem to have the best confo out of the bunch.