I know a load of SPs who are on there too. Thing is, they're often on there as a couple, or just for the swinger events & clubs etc.
One thing is for sure, a meet with a girl from Fabs is going to be different to booking her on AW. On AW, it's all about her making sure you get a good time. On Fabs, it's about making sure she has a good time. It's worth contacting them there first, but due to the volume of messages women get on Fabs don't expect an answer, and if you do get anywhere remember that meets from both sites are a completey different scenario.
It can be good for comparing pics though, and checking for reviews - a lot of the girls who are on both are the ones who do escorting because they genuinely enjoy the sex, so you're more likely to get the sort of service you've paid for.