Dude....seriously.....they're two completely different cars. A Challenger is a massive 2 door sedan, much larger and heavier than a Mustang. In no way, shape or form are they comparable.
You might as well compare an Odessy and an MX5. They attract different buyers, and are in different product catagories. Challengers are, and always were "muscle cars", and Camaros and Mustang were "pony cars", with the Mustang now moving more towards being a sports coupe.
Mustangs and Challengers were never "locked in comparison". Ever. They're totally different, always have been.
Don't you mean coupe? A sedan has 4 doors. Sent from AutoGuide.com Free App