-Zelda U will definitely be 720p/30fps so don't worry about FPS.
-I think there is good chance that NX version have some sort additional features of some sort of additional content (I dont think anuthing big or important would be in that case like new dungeon or something similar).
Personally I am still not sure what version will buy, on first place depends on that if I will buy NX on launch, then depends what exactly differences will be between versions and when exactly they will be launched(I don't think both version will be launched on same day).







