Moren on 08 March 2014
Japan - 3DS by far.
Europe - 3DS. Only because the WiiU version will do catastrophically over there.
America - This will be a little closer. I am going to lean with the 3DS as well.
That is, assuming Nintendo doesn't do something stupid like neglecting the 3DS version in favor of the WiiU version (regarding marketing and content).
EDIT: Also, IMO, if the game had been a 3DS exclusive, it could have had the potential to outsell the WiiU.
