I prefer Air China to Air Canada not only because it's usually way less expensive (I paid around CA$800) for a return trip in Jan 2019, but also because the transit in Beijing let me have a whole night rest before embarking on the next flight to HK. The itinerary is a 12-13 hours flight from Montreal to Beijing, stay overnight at an airport hotel which is around CA$30 with pick-up services (booked on booking.com), then I'll be in good shape to continue my Bejing-HK journey( 3 hours) the next day. It's especially practical when travelling with babies/kids, or the trip is way too long for them.

I stopped taking Air Canada, not only because of their rude services, expensive fare and bad food, but the 14-15 hours flight is toooooo long...