Other things that are different about Katrina and the current situation:
During Katrina, FEMA didn't coordinate with state and local emergency crews, didn't deliver the supplies they were responsible for delivering, made requisitions on resources that weren't available, and in general failed on essentially aspect of rescue and emergency response. In the current situation, FEMA is coordinating with state and local emergency crews, is delivering the resources they are supposed to, and are being an asset instead of a burden.
During Katrina, 2 days after the levees broke, while most of the Lower Ninth Ward was under water and people were literally dying in the emergency shelter in the Superdome, Bush commended Michael Brown, his appointed head of FEMA. "Brownie's doing a hell of a job." A week later Brown was pressured to resign for gross incompetence.
During Katrina, Bush had already been on vacation for 29 days. Obama is in the middle of a scheduled 14 days, which is cutting short to visit on Tuesday, now that the situation has stabilized. The governor literally asking him to not visit until now, as his presence would strain badly needed emergency response crews when they were needed most.
During Katrina, the National Guard was overwhelmed so to "keep order" Blackwater Security Company were deployed to New Orleans. Blackwater was owned by Erik Prince, a friend of Bush's (Prince was a White House intern under Bush I) and New Orleans was part of nearly $2 billion in contracts that the Bush White House gave to Blackwater. You may recall Blackwater from their war crimes in Iraq. Erik Prince, by the way, is currently under investigation for money laundering, suspected dealings with Chinese Intelligence and brokering military services to foreign governments such as Libya and South Sudan. Erik Prince's current organization, Frontier Services Group, is backed by the Chinese state-owned CITIC group and is used to help arrange Chinese investment in African fossil fuel resources.
So, you know, some differences in the situation.