The Legend of Zelda: Between Worlds is probably one of the best handheld titles in the series in regards to handheld game systems.  Zelda: Link Between Worlds was impressive and it managed to sell over 2.5 million units worldwide within five min of its release.  If Zelda: Link Between Worlds was released for the Wii-U instead of the Nintendo 3DS there is no guaranteeing that the results would have been the same.  

The Wii-U was considered to be a commercial failure in comparison to the Nintendo 3DS plus games like  Zelda: Wind Waker HD was mainly the focus for the Wii-U at the time.  If Zelda: Link Between Worlds was released for the Wii-U it may not have sod as much as it did in the long run.