It all depends on what you want to do. If you want to play with competition, your bigger sellers will be lesbian, teen, amateur etc....customer base is very large....just remember, so is the competition...
On the other hand, if you want to corner a smaller niche...that can be quite lucrative. I have found that smaller niches CAN work really well because the audience is very loyal and willing to pay for the 'good stuff'...albeit, the customer base is also much smaller....BUT, again, so is the competition.
