...I think for the most part the better SD's aren't found on those sites tbh.

...but it takes work to find the right relationship.  Generally it costs more but the relationships are usually more like relationships instead of being more transactional.  I'm not saying one is better than the other, there's a place for both but if you actually want to know the person you're intimate with then the whole SD thing can work really well.  

I've had a few successful long-term relationships myself and the best ones have come via Seeking Arrangement.  I'd recommend that site.  PM if you want more details.