Yes and no. After years of training my knuckles, especially my first two knuckles are much larger and more prominent. Punching with a closed fist allows you to stay at further distance from your opponent more than anything except a kick or a weapon. Kicks are often more risky because of balance, and you don't always have a weapon.

Punching also gives you a longer moment arm from the fulcrum, allowing you to hit with more force for the same effort. Of course, you have to be more accurate. A slap doesn't concentrate the force like a direct strike with your first two knuckles, but you can miss by a few centimeters and still connect, which isn't always the case with a punch.

So again, "yes and no."