Oddly enough, I have the same QB dilemma. Right now I'm going with McNabb, for multiple reasons. When watching Schuab, he is almost completely reliant on his receivers to make plays. And against a Bengals secondary that has shut down #1's, I don't see Schuab responding well. Also, for the games McNabb has been in, he's been phenomenal. Now, seeing what Manning did against the Raiders last week, it's hard to sit McNabb, who I personally think is a better QB than Manning.
For flex, I would say Holmes is good for a big play; and who knows, maybe Cleveland will put up a fight this week, after getting their first win?