Just flew HKG/YYZ/HKG one trip AC. One trip CX.
CX much better experience.
Yes starts in HKG with much nicer lounges.
J class on CX is roomy and comfortable. On AC the table does not "disappear" and makes it less comfortable when you are sleeping. It just feels more cramped.
Service is much better on CX. And Food much better on CX.
Also the toilets are bigger on CX and cleaned during the flight.
Amenity kit nicer on CX.