Obama going diverts resources from assistance which is why the Governor has asked him to stay away a few weeks. Workers that should be clearing storm drains instead have to go around inspecting them for explosives with cameras and then welding manholes shut; people that are cleaning streets in the neighborhoods have to converge on where the photo-op would be to clear all trash and debris, police have to be protecting the area for days once cleared and then provide parameter security. The POTUS bubble is insanely time consuming (and a bit excessive). As for Hillary, as long as she says she will spend lots of money she won't really be spending anyway on them, her supporters will cheer and vote for her.
So why was Bush criticized so heavily?
I don't recall him being criticized for that so much as things like the federal relief efforts were held up by them debating whether the officials would be wearing DHS jackets or FEMA jackets. Some of the criticism was unfounded in so much as the Mayor of New Orleans obstructed evacuation efforts by not letting them use school buses
Nobody "didn't let them" use the school buses. That was a photographer's Monday-morning quarterback myth.
Sure because you say so, all the media that reported it was wrong.
I'm a Katrinite.
The media didn't "report" anything like what you posted --- the media posted a photo of drowned buses, and then
speculated about them after the fact. Buses which were by the way outside the city.
In the actual event, Katrina came up fast. I wasn't even aware a storm existed until Saturday afternoon (it hit at dawn Monday less than 40 hours later). That isn't realistically enough time to corral drivers and get buses ready and dispatch them effectively. On the other hand it's the easiest thing in the world to hover in days later, take a picture of something under water and go "woulda shoulda coulda".