If you managed to score an F award seat on the AA JFK-LAX flight (a very award seat to get, BTW), I would stick with what you had. While it is no CX, the F service on those flights is quite good, especially for dinner flights. I've done similar trips, routing on AA to SFO and then takign CX to my final destination. I enjoy the service on the AA flight and look forward to the even better service on the CX flights.