MS had much better planning, leadership and decision making by it's residents. I just don't believe (on a per capita basis) the same number of residents stayed as New Orleans.
Just to be fair, the flood also receeded after the storm everywhere else, in NO it rose. This doesn't excuse the LA or NO leadership but it's an all together different situation.
I think that the difference is that the govenor of Mississippi, turned over the evacuation and preparation for storm relief to FEMA before the storm hit, instead of waiting for two or three days after.