Both pretty good niches, the smoking one you will want to get some video on. one of the paysites with us does teens, and has a live show each week and for some reason the guys go crazy for them to smoke? I myself don't get it, but if it pays the bills who cares
The smoking one might be a little hard to get content, so make sure and have all you need for the first few months! You might check out the plugins and ask them if any of them have any smoking pics or movies for filler. The Tranny you will have a little easier time finding content.
To get started on the billing I would go with ccbill or ibill. Each offer an affiliate program, and I think they each also offer a webmaster referral program on top of the affiliate part. You can also look at plugandpay.com they also offer those types of services, but you have to get your own merchant account, which if your credit is not on top of the world might be a little tough. When you use ccbill and ibill they take care of billing questions, leaving you to run the site, and the 15% they take is not that much higher than if you have your own merchant account when you take into account chargebacks($10 - $20 per chargeback), gateway fee(25 cents - $1 per transaction plus a $10 to $20 monthly fee, includes all tries even if they fail!), merchant account fee's(2.0% to 4.0% plus a $5 to $20 monthly fee), and someone to deal with billing questions($???).
As for the other guys out there, I've seen too many of them come and go to trust anyone other than ibill and ccbill. I lost a ton a money when DMR went out of business, and they were getting as big as ccbill and ibill almost
So I say go with #1 or #2 and forget about the rest
Tim