I prefer the Gamepad since I love the offscreen play so much. Then again, it's the only controller I have for it apart from the Wiimote/classic controller. I've heard the Wii U Pro Controller is amazing though
The only ones like that which come to mind are games where the pad functions as your minimap and shows you were things are such as in Zelda games. In which case I guess having the minimap there would be helpful.