I prefer AMPs.
With AMP I don't have to worry about NC/NS. I have researched the AMPs and know the skill level and the extras if I want to indulge.
This is mostly because I want only L1 and a decent rub. There are only FBSM and there are those with LMT training.
Getting 'off' is my finish and not fake or real passion.
Guess I"m just a Slut; Like both for different reasons - depends on if I have time to schedule an session, or if I just realize I need to NUT and go take care of that at an AMP (or Strip Club; that was easier in the MGM Cabaret/Paradise days of now-old).....
If I had all the required references, I would prefer providers. Since I do not, amps are my method of choice for now.
If I could see this girl: https://www.eccie.net/showthread.php?t=2455300, I would really prefer providers. No references = no go. Might be a good thing because I would end up with no money left over to eat.
It depends on what you like. I like at least a decent massage and a bunch of teasing before the HE. That said, some of the providers' skill levels are off the charts, and some are known for their massage skills too.
I have a couple of providers that are my regulars But I like the unexpected about the AMP's. You never know for sure what your going to get, and I have found that AMP's can be very YMMV if they like you.