Jon, Seth, and Hoji. Most big mountain skiers>Park skiers in terms of racing because they have racing backgrounds for the most part. Nick Martini is the one exception. He apparently used to slay at racing before he switched to freestyle.
Jon because he started racing before freestyle.
Seth, well same reason as Jon.
Hoji has an extremely balanced style, which would prove beneficial for SL and GS. The way he controls his body and skis is impressive.