We have used the Embassy Suites North and the LAX Marriott. Our preference was the Embassy Suites North.
The shuttle buses for most of the hotels are run by the same shuttle bus company and times do vary. Just because you get a quick turnaround one time does not mean that you will get one next time. We chose the Embassy Suites North this time (it uses the same shuttle bus as the Hilton) because we had a bad experience waiting for a shuttle bus for the LAX Marriott on a previous occasion. This time the Embassy Suites/Hilton shuttle bus was the least frequent of the majors at the time we arrived.
The restaurant in the Embassy Suites North - Aero Bistro was very good when we had a meal there - breakfast no idea as we always seem to head off early to the airport and have breakfast in T4 Flagship Lounge.