It all depends on your niches. Generally if there's a good small program in a niche then you want to send it there (but you have to hunt around for them), otherwise send it to one of the larger more generic programs and try to hit the volume bonuses.
For example if you have teens / amateur traffic then single site sponsors like AllureCash, FTVGirls etc are all the rage and will outconvert generic tours from bigger sponsors.
Bigger sponsors I use include Pimproll, Brazzers family of sites, DatingGold, Loaded Cash, Pussycash, AEBN, Videosecrets. I also promote a bunch of CCBill sponsors because they're basically honest and you can combine the paychecks into one payout. Lately I have been sending some traffic to a BrutalBucks site (prolapseparty.com) which has been doing ok. However I'm hesitant to recommend any program because they could all go tits up at any moment.
http://www.signbucks.com/ is a good place to hunt for paysites and breaks it down by niche, payout method etc. Surfing the big tubes is a good indicator of what's selling, as well as surfing the big TGPs in each niche to see what the big site owners are promoting themselves. I also surf thehun.net to find more obscure paysites.
Always a good idea to have a Google for adult programs before you sign up because heaps of them have gone to shit and stopped paying over the last couple of years.
Adult is a tough market these days so don't be surprised if your conversions are disappointing.