I can say I've personally used Dmat xtreme and stinger road kill, both great products, Dmat is over priced if you buy it from dealers, but going to sonic or other online stores not so bad, the stinger deadner I like more since there's no black lettering and looks cleaner. The stinger seems slightly easier to work with, I used cheap scissors to cut both, no issues really. Both are great products. I do plan on buying SS when I do the roof and second layers on the doors, after seeing numerous side by side comparisons and seeing it in person in some locals cars.
from what I've seen in person, fat mat seems like peel n seal with a bigger price tag. FUCKING JUNK the shit falls off deck lids and roofs. leaves nasty stains, stinks and well fuck it lol. Down here on the gulfcoast it gets fucking hot and humid. I haven't seen audio technix in person so I can't comment. But the Dmat, stinger, and SS hold up well. I've had Dmat in my car for 4yrs, no issues.
hope I get money coming in soon so I can order 50ft of damp pro