Green Glue vs. Quiet Rock Drywall

I am about to build a rehearsal studio. New construction, totally detached (at back of my property). Dimensions are 30' x 20' (600 s.f.)with a ceiling peak up to 15 feet. Double wall construction; considering keeping ceiling in 'cathedral-style' (vs. flat ceiling). Top sound isolation important. Two products under consideration (beyond double wall isolation advantages): Green Glue vs. QuietRock drywall. Ignoring budget for the moment, anybody with experience with these products (and, perhaps, cathedral-ceiling construction and isolation)? Many Thanks Colin

I can be very short: please read this forum before you go asking. (I'm not trying to be harsh, but too many newbies these days asking already answered questions while ignoring the forum rules. read them stickies)