I've been using a marsupial w/ 10x42s the last couple years and the only complaint I have is dust getting in the sides and on the glass. As far as comfort, low profile, ease of opening/use and durability I dont think it can be beat.
I picked up some 12x50s this spring and my #1 priority for a case was full containment to protect them from the NM dust. I gave the quick draw a shot because it has some material that comes down on the sides, where the marsupial is open, to in theory provide full containment. Overall I am really underwhelmed by the quick draw. Its overly strappy and baggy compared to the snug fitting low profile of the marsupial. The bino fit in the case was also baggy and loose. Most importantly, the extra side material was pretty worthless in providing full coverage. The material hangs out the sides and still leaves a big opening for dust to come thru. That and I really dislike a case that opens towards me after having on that opens away.
I ended up with the Sitka bino bivy for my 12xs. It keeps out the dust, is super light for its size and fairly slim profile which I like. If I had my druthers it would be a marsupial with full containment. For the time being I think the Sitka will work out fine.