On WiiU, none. It's too soon for either of those.
On the new system; Twilight Princess. It would probably benefit more, is a better game and it's older yet more popular. I can see a TP remaster as a launch game next gen. Skyward Sword would be probematic though because of motion control.
If I had a gun pointed to my head and had to choose one that had to go to WiiU (so, actually answer OP); Twilight Princess again.







