I'm a bit iffy on any RP site that isn't RPR personally since I do a fair bit of mature themes and RPR's the only place I've used that lets you filter out the profiles & characters of minors. (That and even when I'm doing an RP without such things, I just don't feel comfortable playing with someone younger than me, personally.)

All the other sites I go on either ban mature stuff or don't really police their mature stuff to my liking.