Last year, I was travel for work. I used both for domestic flights every month. Air Canada is the worst one. My flights take around 8 hrs. including layovers but Air Canada did 12-14 hrs. twice in a year. These are not including any small delays which usually Westjet has too 1-2 hrs. delayed.
Pro tips: if your flights is delayed, you have to ask their representative.If it causes by mechanical problems, you are able to get compensate from the airline such as $20 coupons for meal covers and discount for your next booking.