I can chime in on the topic at hand, well the OP anyways. I think the Vita is going to fade away and be forgotten maybe not like the N-Gage but more like the Game Gear, whereas the Wii U has the potential to at least reach levels somewhere between Dreamcast and Game Cube, and will make a mid-generation bounce back once the games start rolling in and the price comes down.
I don't know about everyone else but the Vita does not have a single game I am interested in that I can not get elsewhere, but the Wii U has at least three games out now I am aching to buy and at least two more on the way that for me make it very appealing. The games out now are Sonic Lost Worlds, Super Mario 3D World, and Donkey Kong Country Tropical Freeze, the two for sure that have me interested are Watch Dogs and Hyrule Warriors. I know Watch Dogs is multiplatform and I will likely get it on PS3 unless I give in and get a PS4 but Hyrule Warriors looks like the Zelda game I have been waiting for, a game that focuses on the action, and hopefully has minimal side quests. As for Watch Dogs, with the recent announcement they are really trying to make use of the Game Pad has changed my mind about it having potential to be great. I just hope it isn't delayed too far down the road or else people forget about it.