Living in HKG, I fly both extensively. Personally, I prefer AY.

Where AY is better:
Seat & general upkeep of the cabin. CX can be quite worn in places. AY seat is much better for sleeping.
F&B tends to be better (mostly the F part).
In flight service tends to be better (or at least is more to my liking).

Where CX is better:
Inflight entertainment (unless you end up on one of the A350’s where you cannot charge your phone without some feedback noise appearing on the IFE headphones).
Irrops handling - AY is terrible on this front.
Lounges in HKG, although HEL lounges are okay too.

CX has much more frequencies on the routes should things go wrong.