Well I can honestly say that we are free members on aff and sls and we do have about 190 friends on aff and we only use aff for the chat rooms and to post to our friends but as for a free member SLS is the best site out there. We have meet more people from SLS then we have from aff and we even have more friends on aff, just most of them just want to chat and not meet for real.
We have tried to post a private party on SLS but since we are free members we can not post it on there but we can post it on aff so both sites do have their own advantages in their own way I guess. But if your looking for a really good free site then I would say stay with SLS.