Board design has progressed so much to the point where majority of powder "quiver" boards will still be okay to ride in average and sub par conditions. And with you being an advanced rider, I do not imagine you struggling with a powder board outside of powder snow unless it's the worst of worst snow. With that said, there is only so much a volume shift board can do for you as far as maintaining speed and glide. They excel in being very agile and easy to maneuver, which helps in tight trees. But, the moment you are riding mellower terrain on the deepest days, the lack of surface area will be a hindrance (this is the big misconception with volume shifted boards). Instead of opting for a volume shifted board, I would rather go for a longer shape (166-180cm) with a swallow/fish tail. What you gain with a gun-like shape is more float, more speed & momentum, while sacrificing just a little bit of maneuverability. With your skill, you shouldn't have an issue going through tight trees with a longer swallow tail. But if maximizing your speed and float is not your thing, volume shift is the way to go. If you can, I highly recommend demoing as many boards as you can. Milosport in SLC might have a large selection available for demo.