I can't speak to the DR, but the fly on the SS2 comes quite close to the ground. It's nice and provides good protection from wind/drafts entering the tent. In terms of rain, both tents use the same materials and should be equally waterproof. In rainy conditions you tend to get more condensation than in dry conditions, so the SS2 would handle this a bit better as it's a full double wall instead of a partial double wall. You can add a liner to the DR to make it essentially a full double wall too.
In terms of standing up to high winds, I consider the SS2 to be adequately sturdy. I'm sure if you had a tent shoot out in 80mph winds on some alpine ridge then the SS2 wouldn't end up the winner, but it's a solid design that's going to be fine pitched anywhere 98% of the time and if you're really in rough conditions then just put a bit of thought into pitching it in a more sheltered spot.
I've never needed to adjust the height of my trekking poles in the night. Even if the fabric did sag a lot, I could just adjust the tension on the ridgeline guyout lines instead. I normally set my poles at 48" (122cm) when I pitch my SS2, so I think 120cm would be just fine.