The difference between the BP spill and Katrina is that the federal government is/was much better prepared to take care of an incident like a massive hurricane than it is prepared to deal with a much more technical issue like a deep sea oil rig explosion.
In the case of Katrina, the federal government had the experts on hand to deal with Katrina. FEMA should of been able to put protocol in place quicker than they did to deal with the situation, at the direction of the President.
In regards to BP, BP has the experts, they are much more familiar with deep sea drilling than anyone in the Obama administration. The Obama administration's role in all of this should be to give support in any way they can based on requests from the Coast Guard, National Guard, Governors and the BP experts. Along with providing strict oversight to ensure that everything that can be done is being done (which is hard without experts.) They aren't doing enough of this in my opinion.
If anyone should take a fall for this, besides BP, it is the Interior Secretary, whom I believe wasn't pushing BP hard enough after the spill to gather correct information to give to the President to make a decision.
It's a tough situation, because you can pressure BP to meet deadlines and come up with solutions, but at the end of the day you can't push them aside due to the fact there is no other viable alternative.