I would go for a 360, simply because you can get a used phat for pretty cheap at Gamestop. Unless, of course, there are a bunch of PS3 exclusives you really like, and prefer free online. Definitely no point in owning both of those, IMO.
As for Wii U, really no way to tell right now whether you'll "like" it or not, since it hasn't come out yet... I'm definitely going to be getting a Wii-U simply because, I admit it, I'm a complete Nintendo fanboy and need my Zelda, Metroid, and Mario. So unless you are that much of a diehard Nintendo fan, I'd wait for a while after launch to see what the lineup looks like.