I rode the Wednesday years back and it's a good solid regular camber ski but it is basically a park ski and it doesn't give you much all mountain versatility in my opinion. The added rocker on the Soma makes it a bit more playful all around the hill, it's still a pretty stiff so I don't think you will have any issues with stability. If you are set on those two, I'd definitely go for the Soma.
But:
I think the issue you likely have with your prophets isn't the weight of the ski, it's that they are likely mounted quite a long way back which means they'll feel way heavier spinning and flipping. Pretty much any forward mounted ski is going to feel lighter in the air. I have to say, and I think most of NS would agree, you're crazy going in to a season at Snowbird with a 92mm ski as your main ski. If you are keen to stay in the narrower widths, I'd go for the Prodigy, at 136/98/126 they will give you more versatility and still feel far lighter than your prophets. However, I'd look at the Candide 3.0. Next year's ski is a much more stable platform than last year's, with a little camber underfoot and less rocker. They are extremely light and you'll have a lot more fun in that famous snowbird pow.