SDS CLD tiles are the best bang for your buck...http://www.sounddeadenershowdown.com
Peel n Seal just mass loads panels...it has the same effect as a butyl based deadener but it takes lots of lots of layers to do what 1 layer of the good stuff does. Fumes from Peel n Seal are harmful, heat can become an issue and you'll end up with it falling off of every panel you put it on. Deadener is the kind of thing you want to do right the first time and not have to go back and do it again.