You won't get a balanced opinion from this website, the same couple of manic-obsessives with a chip on their shoulder will be onto this thread like a pack of wild dogs, shouting down any kind of balanced opinion or anyone who has something positive to say about certain agencies.
Clue - most of the "big" agencies are big for a reason, i.e. they have lots of pilots working for them, and they're all actually pretty similar. Be careful of brand new and unheard of agencies as many of them are not really agencies at all just a guy with a laptop and a phone, doesn't have the resources to fight for you if you have a problem anyway.