I had a crazy experience renting from Enterprise at LAX and returning at the Anaheim Hilton. They called me a few days later and said they wanted to charge me for a stolen rental car then gave me details for a different car. They even somehow found my mom's phone number and called that too. I normally don't take photos my rental cars but my friend was particularly interested in the car I rented so I had a photo which just happened to show the license plate so I had proof that I had a different car. It got sorted out in the end but I avoid Enterprise after that experience.
I used to like National for the Emerald Aisle but now, Hertz also allows you to bypass the line and is cheaper so I like to go with Hertz and return that at the Marriott. I've also been fine with Alamo one way rentals to Disney but if Hertz isn't too much more, I prefer Hertz.
No matter who you rent from, you'll have to wait for a rental car shuttle from your specific company since LAX doesn't have a consolidated rental car facility. The wait can vary significantly.