LAX hands down. The drive from Burbank, while looking the same requires going over the Santa Monica Mountains via one of the Canyon Roads(Coldwater, Laurel, Bevery Glen) or the the 405 pass, or worse yet, around Downtown. Even in the worst traffic there are good ways to BH from LAX - 25 min on a baaaaad day. (if you want to know the best route, e mail me, be pleased to help out). The rental car drop off is a minor point - unless you are planning a sprint to the gate.
One other option is to drop your car off in BH and take the $20 taxi ride right to your terminal.
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Askworldtraveler, EXP,4 million AA miles+++Hilton Gold (thanks to EXP)