Should I start Brees or Eli Manning?

In my fantasy league I drafted Brees after Rudi Johnson and Travis Henry. Brees really hasn't been impressive and this week he plays the Titans. Eli is playing the Redskins Should I start brees or manning? Also, I'm in need of a WR. Should try to trade Brees, keep Eli and pick up a good QB from waivers? My WR's are Roy Williams, Reggie Brown, and Wes Welker. Brown isn't doing much and Welker I don't think is much in the TD department. So what should I do?