Wu are the best later faction by a long way. Most of their best people don't show up until half the cast is dead.

Also if you play Romance of the Three Kingdoms (Or read the actual novel I guess) you'll see what a bunch of pricks Shu actually were. Zhuge Liang's deathbed wish was to have Wei Yan killed, basically for no reason other than "I don't like that prick".

PR man, it's all about PR.