I just got done using both fatmat and dynamat extreme (had to get the dynamat at a local shop cuz I ran outta fatmat) I cannot tell the difference between the dynamat and fatmat for damping qualities. The dynamat extreme was definately easier to install because it doesn't need heat. The fatmat supposedly doesn't need heat but I didn't trust it to stick without it. The only other difference is the aluminum sheeting on the fatmat is thicker than the dynamat, which I guess is good and bad. The thicker aluminum makes it harder to conform to the sheetmetal, but I'm guessing the thicker aluminum makes a better heat barrier.
My whole truck is deadened now, but have only reassembled my drivers door. I have fatmat on the inside of the outer doorskin, inside of the inner skin, and dynamat on the outer of the inner doorskin. I also made plexi panels to cover the holes in the doorskin and sprayed the door panel with cascade dampening. I now get absolutely no noise through that door! Can't wait to finish the rest.
