For me, Full Tilt Poker and Bodog outproduce just about anyone when it comes to USA-based players. And for players in other countries, Party Poker is hard to beat, even though a lot of people on this forum dislike that program. Hope that helps.
Ultimate Bet doesn’t pay a share of the rake on tournament fees and never have (AFAIK). At one point they said they might start (IIRC), but nothing ever came of it. So if you have players who are going to be playing in tournaments, and you’re doing a revshare deal, that might be something to take into consideration before promoting them. (And if I’m incorrect about either or both of those items, someone please feel free to correct me.)