Factory insulation vs. Dynamat, etc.

I have been using this available at Home Depot in the roofing area. Sticky as hell, way lower price than dyna mat and it is in a roll for long strips. Works fantastic for sound deadening. I have it on the floor of my dart and all over a pickup cab, works great, no smell when it gets hot either. Around 25 for a roll. Not sure how many feet I think 25' x 6"