I fly a lot. 100 to 150 thousand miles a year. It's a deeply personal thing and people tend to react very emotionally and if I may say, not very logically. Taking out the hyperbole is important. I admit to having a large bias, but here are some facts. First, their on time performance is essentially the same. It may range by a percentage point or two one way or the other, but they fly the same routes and deal with the same weather.
Second, SKYTRAX, the most well known airline rating group has their customer service rated exactly the same. Yes, Westjet has some neat things, like their Christmas events and used to be a lot more fun and quirky with safety demos and the like, but as they have grown, they have lost touch with that aspect of their culture. Now they are like any other airline, sometimes you get a good crew and sometimes they are outright miserable. Air Canada has made big strides here and in flight, they are identical, except in AC business class which is far superior to anything WJ does. On the ground, I actually give the slight edge to AC, as they simply treat frequent travelers better. The lounge offering, and status recognition leaves Westjet in the dust. Westjet used to have younger, more attractive crew members too, some real stunners. However, a ton of their crews now are older people, male and female. AC has had a ton of retirements and has replaced with younger people so I actually view them equally there too.
Westjet is a domestic airline, while AC is an international airline. Westjet may be adding one or two Europe trips, and recently got some 767's (not very many of them however) for their charter work and to add some European destinations, but they are not the same at all. Next, 95% of Westjets fleet as a result is the 737. If you are flying business class, it's not even a competition, so I will compare economy. WJ is 3 across either side, they recently blocked the middle seat in the first few rows to make their Plus offering more attractive. If you are not up front or in the exit row, these planes are simply miserable for a long haul flight. The TV has major issues on many flights with connections and you pay for movies. AC has larger, roomier and more comfortable planes. the 777 is a very comfortable plane to fly and the 787 is simply great. The seat are nearly identical in most cases, but the in flight entertainment on AC mainline is free and features movies, tv shows, music and XM radio. The buy on board is identical. Edge to AC on a longer flight, toss up on a short 1 to 2 hour flight.
Schedule wise, it's very clear Westjet targets the vacation traveler, while AC is business airline. Only a leisure traveler would say something like "I don't mind stopping in Calgary on my way anywhere". That's simply ridiculous to a business traveler like me. AC has more direct flights without stops. For me, it's AC all the time, but I do fly Westjet several times a year if needed or it's more convenient for my schedule, but over 2 hours in flight length, it's all AC, all the time. The other item is that they price match, nearly all of the time, so you really have to work to find which combo of service and price works for you, you pay to check bags, you pay for better seats, every airline does it now.
As for Yellowknife, using Kayak or something similar shows that you are likely best off using a combination of AC and WJ based solely on price. It's considered short haul, so I personally would choose on price alone, with a preference to AC because I get lounge access and Altitude credit for my flights. Pick your best combo of time and price and enjoy!