Differences equivalent to CoD DLC does not prevent two games from bein' the exact same game. Smash 3DS and Smash 4 are the exact same game down to their core and play the exact same way, with solely said minor, irrelevant differences differentiating 'em.
I do not think it sensible to release a multi-platform game to boost a struggling console's sales. Especially when the undoubtedly more successful 3DS version releases BEFORE the WiiU version, taking a further chunk of the profits away. And if the consumers end up not liking the 3DS release, why buy an entire non-portable console for a similar experience? One way around this is if they were indeed considerably different games. Complementary.
Also, for you, Bodine