From my experience, the Gatorback is the best belt, but they don't last long. I get about a year out of one before it starts slipping, and I think it's due to the rubber drying out with the heat cycles over that time. The Gates that came with my Magnacharger kit slipped from day 1, and the Gatorbacks seem to hold well for me. If I have a belt slip issue, it is mostly due to decelerating the blower than powering it. It's a lot of rotating mass to slow down during fast A4 upshifts.
