I agree with Sarlacc. Get rid of this QB controversy. Trade Manning and start Brees from here on out (his bye is over). You don't need two QBs, and you should be able to get a really good RB or WR for him. This will eliminate all QB decisions this year.
If you can't trade Manning, and you're stuck with this dilemma, go with Manning this week. Denver's defense is a lot better than New Orleans, and its in Denver.