From what I have read, sorbothane is effective in suppressing resonance only in a relatively narrow band or frequencies...the effects of the EAR stuff is much wider.
I made a 12" round sub-mat for my turntable (I think it was the .125" thick stuff) and it's
more effective than the similar thickness Audioquest sorbothane mat I had been using for the same purpose for many years. It was evident before the first note was played with a notably quieter background.
The sorbothane was very good at this task, too (horrible as a top platter - it is a poor interface with the record itself - but it damps nicely). But, the EAR stuff was simply more effective at it still

That's the clearest (maybe, only) comparison I have been the two products.
More on EAR - here:
http://www.earsc.com/John