You'd be much further ahead at CX, I've worked for both and the disposable income is vastly different. Not to mention the equipment and route structure among other things. Quite simply, CX is a far better company and is more of a finely tuned instrument, AC is an old out of tune bar piano. I would have been on a 320 for years and years as an F/O flying domestic at less than 100k. YVR base would be even longer.
I'd be surprised if the defined benefit pension is around in another ten years at AC. As mentioned, with hundreds of retirements at higher levels, doubtful this will be fully funded in the future. If it is, it will benefit those in retirement, not someone with 20 years left. The wages will be kept low to offset the costs.
My comparison would be for a younger person with mainline, not the freighter option, but even so, I think CX would offer a more interesting career. AC will have better days ahead and it is still a great option, but that's my perspective.