In theory, it's pretty much the same game that's coming out on 3DS, since they're trying to do "transfarring" between 3DS and WiiU saves. So in theory, you could just buy it for your 3DS and wait for something on the console that you *really* want.
Except that unless this has suddenly changed I would need to buy that analog stick addition thing for the 3DS. Or be prepared for the wonkiest swimming controls of all time. But I probably will still get it for the 3DS anyways, which will be sweat since it's the first handheld Monster Hunter to have built in online play.
Well maybe, this announcement video makes it sound like only the WiiU version will have online multiplayer, which drops my interest in the 3DS version greatly if true.