I think under the circumstance, the Superdome was the best choice. Where would you have bussed 250 ~busloads~ of people where there would be better shelter available?
where they are going now, Astrodome, or any where else that could have been rigged. Red cross shelters all over. But out of the area the way people with transportation means were able to exit.
A day before the storm struck there were reports of people with no way to leave. Stuck.
How could the Superdome have been the best choice. God knows what would have happened to the roof if the direct hit had occurred. Reports anticipated the destruction of NOLA -- no electric, no way to return to anything.