NX for sure, although Animal Crossing works so well on handhelds so I don't know, lol.
Latest rumor has NX as a hybrid system, with the handheld version launching this year, and the home console next. That being the case, there's no way an Animal Crossing game gets released this year after just having TWO launched last, meaning if that rumor is true, it's not a launch game for NX. However, if the hybrid is also true, it works perfect pleasing the home console lovers (all roughly 10% of the North American players who actually prefer it that way), as well as the overwhelming majority who want it on handhelds (given how much more it sells in handheld version in Japan- higher than any other region, is also smart).