For me, this one is pretty easy to decide. UA
p.s. all the way. Yes. They don't utilize 762s on this routing anymore, but there 752s that are specially configured for this premium market is a real treat. It almost feels like you're in a private jet and the service is up to international standards.
In regards to inflight service, meals, etc., this too is easy to choose. UA
again. Much better than AA
by any mark. Flight crews seem to be consistently good, not like on AA
where you'll get a decent cabin crew on ocasion, rather than the norm.
Since you belong to AC
frequent flyer program/Star Alliance, you'll get your mileage and I believe bonus miles for flying J.
Let us know what you decide.