Who do you think I should start on my fantasy football team?

I have a little WR situation. Right now my starting lineup for WR's is Calvin Johnson (who's playing Baltimore), Santana Moss (who's playing Oakland), and Robert Meachem (who's playing Atlanta). But on my bench, I have DeSean Jackson (who I'm not sure I should start because of injuries and he's playing the G-Men) and Miles Austin (who's playing the good p defense of San Diego). Should I keep my starting lineup the way it is or sub someone in? Also, which defense is more liekly to score me more points; Redskins D or Giants D? The Redskins have a decent enough D and they're playing the Raiders. The Giants D is inconsistent and they're playing Philly. So who should I play there?