Canada 3000 is a reliable choice for your trip. I would recommend going through YVR because it would sort of break up your trip from the east coast of this great country of ours! Trust me, you don't want to go for a LONG flight with those guys! I'm not trying to be mean or anything, it's just with past experiences with them that I've went to Europe with them several times. They'll get you there safe and sound, which is all you want, but you probably won't be bragging about the service! You get what you pay for...
I believe Canadian flies this route with DC10 equipment from YVR. It's a flip up between the almost-retired DC10 and the brand new A330! C3's A330 is a great aircraft, just don't expect much in the leg room department! I don't think that they could find room for any more seats in there, or else they would!
If you go with Canadian, be prepared to pay a lot more $$$ because of the service thing. If you've got lots of money, then go with CP! If not, CMM would be a safe and affordable choice!
Please don't go through SEA or SFO, keep your money in Canada please!!!
PS... Do I sense a number of Canada 3000 employees in this message board? LOL!!!