787 is a nice airplane, no two ways about it. Just hope you don't get stuck with a last-minute substitution.

The problem with the 737 Max is that the washrooms are about the size of a phone booth, and you will wind up splashing water all over yourself if you even try to use the sink. That's not just Westjet, that's the case for every airline's 737 Max. It's probably the most widely-hated airplane in the skies right now - at least by passengers and cabin crews. Airline management love them because they're cheap.

If you fly with AC, you can collect Aeroplan miles. If you fly with WestJet, the crews are generally nicer and you stand a much better chance of actually arriving on time.

Between those two choices, I'd let schedule and cost decide. What I would actually do though is book Westjet, and fly on one of the flights operated by the older Next Gen 737s (not the Max). I'm also 6' 1" ... seat pitch in the first eight or nine rows of WestJet's Next Gen 737s is a little more generous, it might be 32 inches. You can also try to do a last-minute upgrade at OLCI to Plus seating, which is their version of PE ... it's much more comfortable. Five hours is a long time to be uncomfortable.