Take it from somebody with both: Buy a Wii U.
My PS3 was my primary console last gen. I also had a 360. I skipped the Wii entirely and didn't miss it.
I got a PS4 at launch. So far, the best games are all games I already had on PS3. Tomb Raider, The Last of Us, and Diablo 3. I'm a GIANT fucking fan of The Last of Us. Its my favorite game of all time and even knowing that, I have to still say go with the Wii U simply because you will get such a great value out of it. The games ended up being so much better than I expected and I didn't even realize how badly I wanted one until I had it.
Once you get the Wii U, I strongly recommend:
-Bayonetta 1 & 2 (Duh, right?)
-Zombi U (if you like survival horror, this is such an amazing game for you!)
-Mario Kart 8 (I almost didn't get this because I kept hearing "same old, same old" but its really turned out to be a brilliant game. The track design is near perfection.)
-New Super Mario U (great platformer all around)
-Hyrule Warriors (there's just something fun and innocent about this. Its kinda shallow in some ways, but man it gets hectic trying to keep all your territories under control as multiple teammates are under seige. Plus, dat soundtrack!)
That's everything I have, not counting the virtual console games I've bought, and I'm just loving it. I'm so happy to have one and I had no idea it would be this awesome. I just wanted it because my buddy was comparing Zombi U to Dark Souls and telling awesome stories of survival. I got so much more out of the system already, I'm really happy. I think you will be too!
*Edit*
I see OP has decided on the Wii U. Great move! Enjoy!