I feel like the 3DS/Wii U should've been handled differently...
some features were left out of the Wii U because of the 3DS's limitations and likely because of the extra time needed to port shared content, Ice Climbers for example, Break the Targets I felt was left out due to time as it requires time to create a separate stage for each character...
The 3DS version I felt should've been a stand alone Smash game, didn't need to have 50+ fighters but at least it wouldn't seem like it held back another version of the game, which could handle more than it could...
during the ESRB leak I always thought that some characters like Duck Hunt and Bowser Jr. would've been 3DS exclusive while more characters, including the Ice Climbers, would've been added to the Wii U since content in every other aspect of the game wasn't fully shared between the two...and the more simplified single player would've been a better fit for a handheld...
I love that it's on a handheld but after getting the Wii U version I rarely ever play the 3DS unless I go out an about, but since I'm usually busy doing something or driving I don't really get much of an opportunity to actually play it, and while at home I have the Gamepad, soo...the only reason I put in more hours to the 3DS is because I've owned it since it was released and I only just got my Wii U last November...probably would've had more incentive to buy it sooner had it not been on the 3DS or had it actually been treated as a separate title, which to me is a huge factor why the 3DS sold better....plus more people own a 3DS than Wii U regardless...