Well, let's see:
SCC has two great freeleech sections (MP3/0-Day and the archive), which you can use to buffer your account up once you join. If you're into that, the pretimes are very good as well, and there are a bunch of members with seedboxes which keep downloads speeds zippy. On the downsides, seeding non-freeleech stuff may be somewhat difficult for that same reason if you don't have a fast upload speed. Also, retention for stuff that isn't part of a pack is rather poor, and they don't track P2P releases, only Scene stuff.
GFT... never been a member, so I'll tell you what I've heard: it's ratio-free and uses a more "democratic" system for promotions (combines seeding time with the amount of snatches, if I remember correctly). Pretimes and speeds are good as well, since they have an auto-upload script (well, most sites do nowadays) as well as seedboxes. However, retention is poor.
RevTT... another great place, and the one I'd also pick from the three. They have lots of members, making speeds and retention very good, pretimes seem to be OK (I say "seem" because I don't care about pretimes at all), and they also track P2P releases, I think. A great site, and one I've used a lot back when I was relatively new to private torrenting.