I said it around E3, but I personally preferred the idea of Killer Freaks more than Zombie U. I enjoy satirical, silly shooters that don't take themselves too seriously, and I was under the impression Killer Freaks was just that. Kind of a homage to exploitation cinema, with a crazy protagonist fighting silly gross aliens. Basically a non-on rails HOTD: Overkill, with mutant Rabbids. That to me sounded cool.
Zombie U is doing some cool stuff with the GamePad and I like the focus on survivability, but stylistically it does nothing for me at all, nothing that hasn't been done before in games that I find more interesting. So in that respect I do wish it had gone for something a bit more original and interesting, as I found Killer Freaks, and not just 'another' serious Zombie game.
A serious Zombie game is probably easier to market though.