I would go with Palmer, even though he's not a clear-cut winner in this "conundrum" as you call it. The matchups for these QBs are not good at all. And even though the Steelers' D is very good, Palmer has been playing better than all of the others lately.
Tough choice. I would say Palmer but I have a hunch the Steelers passing D is on the uprise, and he didn't do all that great against Pittsburgh the first time around...I would suggest maybe looking at any available free agents and see what kind of matchups are out there? Else, I would probably go with Palmer.