AC flights are already codeshared with CP between YEG and YVR, and are operated by CP with their fleet of 737s for the most part. And even if they weren't, it doesn't mean your bags can't be checked right through to HKG. Most airlines have interlining agreements with one another, irrespective of their other alliances.
As for Y-cabin comfort, both CX and CP are pretty much equal from my experience, though CX often flies its older 747s on this run. With the DC-10s all gone, Cdn's fleet is made up of pretty new 747-400s.
Your real issue is what program you are having you miles credited to. I assume you are a Cdn+ member, and if what you say is true about the end of oneworld for Cdn comping in July, you have no real choice. Starting a new FF account on CX wouldn't be of much use, since discount fares don't received credit. Same with discounted CX flights on AAdvantage.
[This message has been edited by Shareholder (edited 02-21-2000).]