I've tried both and think they are both good skis.
Personally out of those two for powder I would go Obsethed (I am a charger).
My Stats
5'9''
135lbs
I ski fast, aggressive, will be doing freeride competitions in the future, and stick to off-piste terrain.
I am currently on the 2008 168cm Volkl Gotama, which is far too short for me.
183 Bent Chetler
I understand now why this ski sold out in December: it's that good. This was the most playful ski, along with being the lightest. Coming from a 105mm ski, I was impressed on how it doesn't feel like a really fat ski on groomers. On my groomed run, it performed well, with some slight tip flap when I was going fast, but still felt stable. I was able to do any turn I wanted, its especially excellent in shorter turns. In the powder and crud the Bent Chetler held up extremely well, and was lots of fun to be on. High speed straighlines were the Bent Chetler's worst skiing, and it did ok. This ski is a playful skiers daily driver.
179 Obsethed
I came to the demo wanting to try a variety of skis, with differing rocker and flex patterns, so I came to the Obsethed for the super soft ski. Honestly going in I had low expectations, and was blown away. First of all this ski is scary soft, especially in the tip, and almost the entire ski is rockered. However, it's stable and fun. The rocker did chatter on groomers, but in off-piste snow it was pretty good, as long as I stayed out of the backseat. All turn types were possible, and the Obsethed was excellent in softer snow. This is too soft for a daily driver, but it was a good ski, including the graphics . I think this is what the S7 intended to be.