I think the call is best made on status and frequency of trips to Asia. Basically in Y, with United you have Economy Plus if you have status on any of their planes, but you have a guaranteed in seat TV on AA while on United you are guaranteed a 747 into Shanghai. I would consider the meals in coach to be equal on both carriers, but IMO AA has a better alcohol selection. If you are flying in C, I would choose AA right now, because of their newer seats, but when UA starts running reconfigured 747s on that route, I would choose that over any of the current competitors on the route.