Catzatsea/Coyne
If Catz is getting in at 6, with immigration, baggage, customs, I'm not sure he'll have enough time to make a 7:20 flight. Plus US is over in T1 with WN, and sometimes the security lines can be quite l-o-n-g. If you have a choice, I'd suggest the 9, you'll have time to take a leisurely walk (there's also a shuttle you catch on the lower-arrival level) over to T1, get a cup of coffee and relax between flights... breathe some of that nice L.A. air.

LAX terminal map

Keep'em flying