I don't have first hand experience with either, but know folks with the Durston.I prefer Dan's setup, and I believe he was the originator of the design. While both are 20D fabric, the Durston has a 2500mm sil/PU coating vs. Sierra Designs 1200mm Sil/PU coating. Also, the Durston has two actual doors (rather than the partial/gear door of the SD) and has bigger vestibules and great fly coverage.

Yeah, The Sierra Designs is fugly too!

“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away” Antoine de Saint-Exupery