with the crunch you kinda just "curl" your upper body up, instead of sitting up. You also don't let your lower back leave the floor. Many feel that the exercise doesn't work the abs like they are "suppose" to be worked. If you wan't size however, I'm sure crunches can help you, but 200 won't do anything. You need to keep the reps at about 8-12 for size, when you can do way more than that, it's time to find a harder exercise or make them harder by adding weight.