I'm another who thinks all the best surgeons do a great job on a good day (and there's never any guarantees about a bad day, for GRS or any other specialty).
FWIW, I went with Brassard; no horror stories from me, the people in residence at the time with me, or a couple of friends who've gone after. But I'm sure there *are* complaints out there; every surgeon has them. (As for the results, it passed flawlessly after a pants-off exam for a nasty GI bug in the ER, when I was also coughing so much my voice sounded awful. And my GP says it'll look fine internally too once the last scar tissue fades.)
As for criteria, if it helps, my approach was to choose and then rate the major "features" : I wanted sensation, then appearance, then functionality [lubrication, etc.], then depth. And that's exactly what I got with Brassard, but someone who prioritized depth higher should look more carefully elsewhere, for example, because he typically offers 5.5" and then uses the remaining tissue to enhance the external aesthetics.
I didn't need FFS, so no idea how to shop for those surgeons.