The early AM TPACs knock me out. The AC15 is a great slot leaving at 10 AM and arriving at 1.25 PM (or more likely 2 pm). It gives me the time to connect or to get settled in at the hotel. However, the CX 826 at 3:25PM that gets in after 7PM is an excellent time as well.
It's all about trade offs. I do prefer AC despite some negatives. My experience has been;
Food and beverage: CX is better. The attention to quality is still there. At Air Canada it is the same old boring uninspired industrial cafeteria fare. Despite all the hype about Signature Service, the quality hasn't improved.
Cabin Crews: Depends on one's preferences, but I would call them equal. Each has positives.
Cabin Experience: After several years of being wedged under the tray table of the AC seat and not being able to sleep comfortably on my side, I have come to dislike the AC seat. My experience with the CX 777 is that it has a pull out tray that allows for a roomier feel. The assumption that the AC seat gives more privacy is wishful thinking. No matter the design, once the lights go down and people go to bed, the difference is minor.
I hate warm cabins and CX can cook you. One of these days, I will drink one too many portos and forget I am on a flight and will strip down to my undies and give the cabin a traumatic encounter.
CX keeps its lavatories spotless and they are a more pleasant space than the stinky AC lavs. All I know is that there must be many physically disadvantaged/impaired males who fly AC because they leave the lavs splattered with urine. (Sorry boys, but I don't think the girls stand there and spray the toilet and floor.)
In respect to the lounges, unless one is connecting, I doubt that most people spend too much time in the YYZ lounge. I know I have better things to do. Sure a quick drink or a nibble, but that's it. The YYZ lounge experience whether it was AC int'l or PP, was never anything to celebrate. Yes, the Hong Kong lounge experience is good, but I find the CX experience over rated. The lounge is often crowded and noisy. Whoopdeedoo, you can get pizza. They have food and nice drinks and you can have a headache too from the packed place. On the other hand, I can pick between the busy TG lounge with its Thai menu based lounge or the updated United lounge which is always empty when AC pax are there. I detest United, but it has a good lounge in Hong Kong. Fresh food and pleasant staff. Because I love Thai food, I often visit both lounges and have my lunch with TG because I know that the AC meal will not be particularly appetizing.
However, I now select based on cost. If I leave on an off peak day, I save money by flying AC. If CX is less expensive than AC, I will select CX. (I don't even bother collecting points with CX or OW.)