Ah, the classic youth versus experience trope. It dates back to Zeus and Chronos.
In one corner, we have Erik Coleman. Signed away from the New York Jets in 2008, Coleman has been effective against the run, mediocre against the pass and generally an alright starting safety. He was signed to bridge the gap between the Bobby Petrino era and whoever our next young study safety was, and he's done that. If nothing else, we should applaud Coleman for consistently being okay.
In the other corner, there's William Moore. After missing all of 2009 with injuries, Moore was no lock to provide value in 2010. Given a Coleman injury, though, he jumped in to starting against the Cardinals, made a couple of nice tackles and picked a pass. Just add water and you've got a safety controversy.
So who starts against the Saints?
"I thought for his first action, he was very, very solid."
That's not a ringing endorsement, though, and the Falcons were openly talking about not trusting Moore in the week leading up to the Cardinals game. They'd like to see him seize the role with authority—and for my money, he took a significant stride Sunday—and go with Coleman in the meantime. The stopgap option is sometimes surprisingly difficult to unseat.
Unfortunately, we won't know until near the end of the week if Coleman's healthy or not. Against the Saints' aggressive offense, I'd rather have Moore in there, because in my mind he's got much more potential against the pass. With the Saints potentially missing Reggie Bush, we're going to have a lot more to fear from the Black and Gold through the air. Moore also seems more likely to pick a pass, though I'm basing that on the smallest sample size possible.
So to answer the title of this post in the shortest way possible, Moore only remains the starter if Coleman isn't able to play. Since that's looking reasonably likely at this point, I'd brace yourselves for more C4.