Traction > power.
You could argue that the GTI could leave you in the twisty national parks, especially with DSG.
I like the S1 because of the short wheel base and small footprint, which means I can enjoy the road more because I can adjust my line.
The buying process at Audi was much more enjoyable than VW.
I think depending on the area, re-selling the S1 would prove to be quite difficult.