SSB easy.
A new full SSB game vs. a collection of old Halo games? The WiiU has a larger install base and unlike TLOU:R it's not like the Xbox One has a bunch of gamers who never had a chance to play the halo games before.
I'm sure both will sell well, but I don't think it will be that close.
Edit: anyone know if there is going to be a SSB WiiU bundle?
Bet with Adamblaziken:
I bet that on launch the Nintendo Switch will have no built in in-game voice chat. He bets that it will. The winner gets six months of avatar control over the other user.