Thread likely going to be moved somewhere...but in before it does.
I'd say right now Merge (Carbon, Aced, etc.) or Revolution (Intertops, Lock [if you REALLY don't care about cashout times, their funds are on the cheap in P2P trading], etc.) in terms of amount of games and decent RB. Though with Intertops their RB/loyalty system is a little different - more experienced folks can describe that; and 'Tops is invite-only for US players, as well.
Yeah...I'd play a lot more on BCP or ACR if they had a better spread. Too many high buy-in, low GTD games save for the nightly 10k for my taste.