I dont think there is any doubt that secondskin's damplifier pro is the best performing mat on the market today. But, its not the best bang for your buck. That's what I generally chose to use, but if/when budget becomes a concern Id turn to RAAMAT.
I have previously used several other spray-on/trowel-on deadeners like Stinger roadkill, RF noisekiller. Up to this point, RF's has been my fav, but way too expensive. I have a couple gallons of SS spectrum V2 sitting around here Ive yet to use, but I have high expectations.
When I really want to mass load, I have a concrete mix I like to use.
Closed cell foam and carpet backing work well for blocking/absorbing unwanted noises.
Fiberglass placed strategically is a low-weight way to stiffen large panels (like a roof).
Closed cell expanding foam works for both stiffening and sound absorbtion.
The key to good sound deadening is understanding your goals, and how to meet them, and applying the proper materials and techniques. Not using a mass loader to try to block road noise, for example.