A couple of things: first, you should look into the planes used by each airline to fly the route. You don't want to pin all your hopes on upgrades only to find out the equipment is economy-cabin only. Of course, it also depends on which schedule works best for you.

If I were you, I would apply for the American Express Platinum Card (yes, with the $699 fee) because you will get Cathay Pacific Marco Polo Gold status immediately, which will serve you well while you're accumulating enough miles to earn status the hard way.

In addition, the Amex Platinum will get you free access to the new Amex Centurion lounge at DFW, and the CX Gold status will get you into the AA Admiral's Club in both DFW and YYZ.

You can decide either way on AC or AA (or both) but at least the Amex will make that first year or two a lot easier on the oneworld side.

You can PM me for a referral for the Platinum card so you can get get the big sign up bonus, or you can use someone else's link in their signature. Or you can apply on your own.

You can also look into the Amex Aeroplan Platinum if you decide on AC, but I personally don't think its as good a value as the regular Platinum card.