Never experienced CX or AC J out of YYZ, I do a YVR-HKG twice a year, if price is the same I take AC over CX, I tried CX a couple of years ago when they had a sale and I find their service quite cold compared to AC. Seats are pretty much the same to me, you get a little extra privacy with AC seats. Food wise, I think its about the same. If the lounge is your thing, then CX lounge in HKG is miles better than any AC lounge I've been to.