Personally I think FreeClassifieds.net would hold more value. Everyone's used to saying "Classifieds," and not classified, so whomever would purchase or use this domain would lose a significant percentage (not necessarily amount) of traffic to people typing the "s" at the end (on this subject, most traffic is likely to come from word-of-mouth locally), and would go to the other already developed site (FreeClassifieds.net) by mistake.