Extending the belay device makes getting your hair caught less likely if you have long hair. When I rappel off my belay loop, the ATC is at my chest, right where my pony tail swings over my shoulder - I got it caught once. Now I extend the rappel so the ATC is about eye level. Also, when you extend, I think your body is further from the device, since you tend to lean back slightly as you rappel.
I have a PAS, but when I retire it, I won't get another one. Now that I know the frost knot, I will tie the same thing as the PAS out of webbing, but use the frost knot to make the end loop, that way I won't have an extra knot in there to close the webbing. I rack my PAS by clipping the first and 4th loop, then between my legs and clip to the haul loop. People always ask me if I meant to do that, but it works great