Plummer is on Thanksgiving day and Big Ben is on Monday Night. The PIttsburgh offense has been offensive without Ben and Indy showed they're capable of giving up a lot of pass yards. Ben has had two TDs in every one of his starts. But it's at Indy where their defense is a little faster on the artificial stuff. Plus, Ben might not be 100%.
OTOH, Plummer is playing against a good Dallas defense.