NR was the best site as I think it attracted better quality women, and better quality men. The layout gave a lot of good information as clients and providers could discuss things in public.
BP has a larger pool of people accessing it, but there's very little quality control. It is common for a woman to use someone else's pictures and there's no way (using BP alone) to know if the woman is legit or a scammer. BP is the wild west.
USASexguide.info has a pretty good community of people but I really hate how all of the information is in one long stream. You can get information on BP and NR ladies but because it is all one thread you have to talk around multiple other conversations.
P411 was nice but they changed some things recently. I was never a paying member so I don't know if the "activities I enjoy on my own time" section was removed or just reserved for paying members. I do know one provider said she had a lot of work after opening a P411 account but I don't know if that was sustainable or if the people there were just eager to see a new girl.
ECCIE has the best layout. I like how you can click a provider's username and see her profile, with contact information and reviews. I just with it had a photos section.
Hopefully people will migrate over here now that NR has tanked.