Schaub is a better choice in this one, Brees have no running game so the def. will be playing pass pretty much all the time against the Saints. Texans have a couple of backs that can get the job done to open the passing game.
I would take Schaub over Brees, the loss of two of his top targets (Johnson and Jones) didn't seem to effect him last week with Andre Davis looking good filling in at WR, and the Saints just look plain awful to me (just where is Devery Henderson this season anyway?). Though given Schaub has the same bye week as Romo, you would still need to look at another option for week 10, Brees has St Louis at home which could turn out OK cos if anyone sucks as much as the Saints this year its the Rams, though I like Trent Green of Miami against Buffalo at home in week 10 better right now.