If I sample where they are advertising, from my experience, sort of off the top of my head
BP providers 50% reliable
Eccie Verified Providers 100% (i actually have a higher cancel rate because of my carreer's interference)
UTR 75%
I have one provider, that is really great BCD, but totally sucks at scheduling, and so if she has a scheduling snafu, I know a few providers that can "quick schedule" in case I need really need to get my rocks off. But don't tell them they were second choice LOL, i did that only once.