Fly. Imagine the millions you could make playing sports. Football they could just hand it off to you and then you just fly into the end zone. It would be pretty easy to block extra points and field goals. Basketball would be lob city every play. In fact, technically, you could make every shot a 3 pointer as long as you take off from behind the 3 point line.
Granted, running 100MPH would be advantageous in its own way as well, but there is potential for more contact, and its not clear how this running works. If it requires no real effort and you can move in all directions just as fast like The Flash then it would be a harder decision, but I think you could impress more chicks by doing the Superman fly them around the city thing.