BitTornado isn't very good, especially with multi-torrent management. It's basically as bare-bones as you can get without having to go with the original
Azereus is good, but i find that it hogs the line too much compared to the others. However, the amount of memory it uses for 10 torrents is about 10x less than BitTornade with equal amount open.
I haven't tried the others.
I use BitTornado since I've always seem to have tracker-update problems with azereus (that and it hogs my line). However, the good thing about Azereus is that it keeps stats better and seeds the things that needs to be seeded. It's done very automatically per-user-settings, so you don't have to watch your ratios like a hawk.
if you're a u/l-inux user, then azereus is the only way to go.
