You're basically asking, if I added a site to a premium AEN/AVS would I get double the signups.
Or, how long is a piece of string.
You have to consider other things, if you made a solo site, your biller would take 10-15%. You cannot sell the fact that if you purchase access to this site, you get access to 100's of other sites. You have to pay for hosting...
The AEN system is a fantastic one for new and experienced webmasters, as the AEN company does all the hard-work for you.. gets the content, gives you hosting, some of them will promote you. They take 50% some take less,
http://www.adultsallowed.com/wm/index.php/3990 [AdultsAllowed] takes 40% I believe, and pays $14 on each signup.
http://www.adultbouncer.com/webmasters.php?wref=ab19855 [Adultbouncer takes 50%]
The disadvantage of the AEN system is that you do not have total control over your box, so you can't put mail on it, or view webstats. I believe what the AEN network takes is more than fair however, considering they are paying for your content, and hosting. All you have to do is promote.
I personally think the AEN system is great, and although visa is being an asshole about the AVS/AEN it still performes great!
Hope that was helpful ^^