How they compare
Both are hookup and casual-dating sites with paid memberships.
AdultFriendFinder is the longest-running and best-known, closer to an adult social network with chat rooms, member content and live cams. Messaging needs a membership: about $40 for one month or about $20 a month yearly.
BeNaughty is more straightforward, and its free tier lets you send a handful of messages a day and receive unlimited messages. Monthly membership is expensive, so its short trial and longer plans are the better deals.