Well lets have a go at it shall I?
Base preference: Vancouver (or Hong Kong if CX) #1, Toronto #2. You meet the requirements for a Freighter F/O but you could also join as a Pax S/O. As a Freighter F/O you will be NA based for 3 years following training at LAX, JFK, ANC. You will have to commute if you decide to live anywhere else on your dime. After training and the 3 year time on frieghters you could transfer to pax and apply for a YVR base. Total time from hire to a YVR base if available would be about 3 1/2 to 4 years time.
Or, if you joined as a S/O you would be in Hong Kong for the first 5-6 years approx. till able to bid for a base. This would be the best approach if you want YYZ as you could try to get a Airbus assignment when going for JF/O.
Pension = ? Which is the better of the two?
CX doesn't have a pension but they pay you 15.5% gratuity every month which you can take as cash or invest in a restricted mutual fund family. AC has a pension but we have seen what can happen to pensions if an airline goes bankrupt...look south!
Pay = ? (Overall, I mean. The first years are known but will one pay better than the other in terms of pocket cash? Taxes a big factor, of course.)
CX is much better as AC takes many years to catch up and even more years to make up for the loss of revenue in the first 5-10 years.
Time to command = ? All I can find out is at CX it is about 4 to 5 years on the freighter side to command. AC = ?
Freighter command can get very short especially if you're interested in a B747F in Europe. 4-5 would be about right for a B744F command if you make it through the hoops. Pax command would be about 9-11 years. AC could be 25+ years if you want a YVR base command.
Which to choose? Well, I think that is up to your needs and personality. Do you like to live as an expat? Are you looking more for the excitement of living abroad with good pay and many options or would you rather have total control of your schedule and life? I'm with CX and very happy but some find the schedule and the operation very frustrating. If you never plan on going to Hong Kong and living abroad, then go for AC. But remember, a non-resident gets to pay NO CDN TAX and HK tax can be as low as 8-9% for a family making less than 1 million HKD.