IMHO AC's based on one longish flight (LHR-YVR) and one short flight last year on AC their flat-bed hard product is significantly superior to UA's and we found the service and the food on our only TATL trip also to be superior as well. Others with more experience can do doubt offer more informed opinions.
We flew one way in AC's Economy and found that to be superior also, right up the ice cream bar served toward the latter part of the flight. ^