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Chesty can deliver some good footage in deep pow, it gives a bit more context as you get more ski/legs in the shot and actually get some frame of reference for just how deep the snow is. Helmet mount doesn't show that quite so much unless you angle it down so much that you can't see where you're going in the footage.
Pole mount is king for pow and general skiing but tricky to make workable for park (filming yourself that is) likewise with chesty it's just a flailing of arms and movement because your upper body is obviously a lot less stable when you're throwing spins.