First of all, there's no denying that a
deep squat will
recruit more muscles and burn more calories, so it offers bigger gains when compared with its parallel counterpart.
Let's say you are going to be doing 20 slow controlled
deep squats, where your core, your back and every muscle in your body is engaged to it's full potential,
recruiting more muscle fibers, it is a lot harder then it may seem to perform every single rep in that perfect form.