Racers/racestyle don't rotate their upperbody, their shoulders, or their hips. The movement is only up and down from the legs and flexed ankles. Rotation style is mostly used with push and pull technique, especially with (extreme) carving. So just depends on your style you want to ride with. None of the styles have their butt out, both work with flexing the lower body and keep the upper body straight. A couple of years ago there was a topic on this here too with many technique vids.