I'd sell Iron Man before I sold TNA. Of course, I've owned IM a good bit longer, but at 8 months, TNA isn't really in the honeymoon period any more.
IM, it's all about trying to line up all the modes during a single ball. Mess that up, and the game can feel unrewarding. TNA, I always feel like I can salvage a game that's not going like I want.