I had made this thread a couple of years back when I was looking at purchasing a new car, and I ultimately settled on the Camaro. I liked the fact that not many people drove one (relative to Mustangs and Challengers), and it was cheaper than the alternatives when comparing trim levels.
While I do really enjoy the car, I do regret puchasing one. Visibiilty is abysmal, and there is very little rear passenger and trunk space. In fact, I don't think an adult can get into the back seat. Out of the three, the Challenger had the most "usability" factor, and wasn't materially smaller than a mid sized car like a Camry. The Mustang probably offers the geatest bang for your buck if your interested in performance - a used 2019 GT premium can be had for less than 40K (Canadian) and your getting 460HP and some nice comfort amenities (leather seats etc.).
To be honest, if you want a pony car, all three have their appeal. I still think the Camaro looks the best of the bunch, but if you plan on using your car for day to day activities, I would probably look at alternatives.