When you promote an aen site...
 

Should you really push the fact that they're also getting full access to over 100,000 other adult sites, or push your niche content the most, and just make the 100k other sides kind of a side note.

I dont know what the trigger is that gets the sufer to buy, if the tour just wets their appetite and the 100k more just brings them in, or if they dont care about all the other sites.
IF thats a BIG feature then Ill add screen shots to other sites

Are you talking about AEBN?

Either way, it mostly depends on your own traffic. If you have a site in a relatively rare niche (like midgets), the fact that they have quite a few full videos in that niche will appeal to the surfer.
If, on the other hand, you have a generic site with mixed, generic traffic, the prospect of a vast quantity of content including lots of niches may prove more appealing.

Best thing you can do: experiment, and see what works best for you.