I don't have much experience with high level play in this game, but DMC4 takes the mechanics of DMC3 and elevates it with style switching, physics, and just more stuff to do in combat in general. On the other hand, the game has annoying level design and a baffling structure that gets worse on Dante's half. I'd also go so far to say that its bosses are a lot weaker than 3, although still solid. If based on pure mechanics, 4 is definitely better than 3, but otherwise I think 3 is better.