OT reply:
Your a risky one mate, all consoles are relatively new, all have their cons and pros though here a short guide on how and what:
Question one: What games do you like?
A. Sony Games like Uncharted, Modnationracers, Gravity Rush(great game!!) etc.
B. Nintendo games as in Zelda, Mario, ect.
If you've answered 'A' at question one, try looking at the Vita's game library and announced games, it is very small and third party companies are not ready (yet) to support it. I love this console since I own it. I love playing Uncharted but I feel a huge 'new game' drought right now with the console, I haven't played it in two months right now. I think you should wait until the PS Vita develops a more stable library and then you should buy it.
The same goes for Wii U, although this one is a bit less risky since it is Nintendo(If I know them right, after they released Mario Kart and Smash Bros. it'll be fine.) But there are many games in development for Wii U right now, Nintendo has announced titles like Bayonetta 2, Lego City Undercover(I have my doubts though) and many more of course. And you already have a lot of great games(lol no to much, the Vita has more), Nintendo Land is a lot of fun with friends, New Super Mario Bros. U is a great game also. But you'll also find a lot of ports, and some of them are a real pain, trust me. I also own this console) I also can't wait for Pikmin 3!
The 3DS is a pretty stable console although all the shit going on about that 'hack' right now could risk the third party support because of back-up loading. But the 3DS has a more refined library at the moment, Mario, Mario, Mario, Zelda and even more Mario. There are also a lot of cool third party games and a special one too(for Emigre) Tom Clancy's Ghost Recon Shadow Wars. There are also a lot of games in development for this console, including shitty shovelware
the DS had plenty of that... But still we also get games like Smash.(hey a real fan you know)
If I was you, I would go for the Wii U, since it is a next gen console and I feel that the future holds a lot of awesome games. You should try to get both 3DS and Wii U when Smash Brothers. comes out!
As for the Vita, try to wait until it's library is more stable, I ain't sure but it seems like some third party developers are giving up on this beautiful handheld.
And we didn't look at the specs of all console yet.(Since this is really not important)
My main point is: check the upcoming games and the games out now and try to find out what console and console library suits you the best!