Compared to the Gnarkosi they are slightly lower volume in the heel (smaller heel counter/lower center of gravity) Grip they are better (its Stealth rubber, duh) Side by side it would be a tough call.
I have now witnessed bootie beers drank from both the Gnarkosi and the Brewer, and the Brewer fails in that department hands down. The poor kid had to drink a 2nd boot to redeem himself for the failed first one.