I have the same choice on defense, I'm leaning to the Bengals as well, but I have the same thoughts re: the turnovers. I keep coming back to the idea that the Browns offense really is that bad, and their success against Detroit might even cause them to take a few more shots down the field, so the sack/int opportunities will be there. That purple d looks really tempting though, doesn't it?
Another tough choice at RB, but I like McCoy slightly over Mendenhall, if only because he stays involved in the passing game. The Ravens are a tough matchup for Mendy. I don't think one is clearly superior to the other given who they're playing. Good luck!