I have not used Dynamat, but last summer I did a complete install (78 Midget) with B-Quiet. It is wonderful stuff. Huge difference in noise reduction. I can actually hear the radio.
Removed all carpet and pannels. Removed OEM sound damper from tunnel and foot wells. Scrubed very clean; very happy w/ no rust. Had a little bubbled paint below drivers heals and seat rail contact points; hand sanded clean, treated w/ rust stop, primered and rattle can top coat for more seal. B-Quiet rolled on extreamly well. Molds easy to irregularities on floor and covers comples curves. Covered 100% of interior metal. Much noise comes from firewalls.
B-Quiet is visually similar to Dynamat. Easily pealed paper; a layer of a black tar-like material that sticks very well to clean dry surface; topped with a layer of very thick tin foil. Suggest going to web sites for both products. I was surprised to find both companies show certification test results to ASTM E756 at 200 HZ. B-Quiet.com has a Comparison page that shows their product is slightly lighter, slightly thinner, and is slightly better accoustically than Dynamat, yet it is less than half the price. I was skepticable. I was also surprises to see Dynamat used the same numbers in their tech data.
I am now a believer. Cost for 50 sq ft is $130 plus shipping from factory.