In general I haven't found big differences between one company and another, except for flexibility in renting, rates, etc. I've used Budget, Avis and Hertz and LAX. I'd rate them all about equal. Can vary by day (determines availability of cars) and the particular person I dealt with. Personally, I'd return the car before 10:45 since the shuttle to the airport could be delayed or slower than you thought, it could run into traffic at the airport (it happens, even late), and I always prefer to have over an hour to check-in, get through security and get to the gate. Jetblue seems to use Terminal 6, so you could have many people getting off the shuttle, with several bags, before you. At thathour, fewer passengers than normal, but several could be international (i.e., more bags). Enterprise gets high marks on the Lonely Planet Thorn Tree bulletin board. I have used them only once, since they don't normally allow one-way rentals and many of my rentals are.