I know for us
www.69toplinks.com that we have categories for those. If they fit into multiple cats, I would say go on your gut feeling with each site and what it's focusing more on...for example, is it promoting anal only sites, porn stars, mix of hardcore, just facial content...etc...then that should help you determine which link sites (categories) to use. If I see a site that could fit into another category that is limited with sites, I will accept or even move the site to that one.