The thing I'm finding so far is the format on all these other sites just isn't as good as BP. It's nice to see all the advertising on EC, but with so many girls there it's some work to sort through everything, the thumbnails are way too small, and the copyright protection makes it more difficult for due diligence. LL is slightly better, but still not as organised as BP and the scammers are starting to flood in. PERB works well, just wish there was more of a selection.
I think a great idea would be a central site that links to all the escorts (by city) that have their own websites.