There has been the argument of size when it comes to hand to hand combat, and it still has not stopped. You’ll see people say size doesn’t matter, and then people saying there’s a reason why weight classes exist. There is one undeniable fact, and that is size is an advantage. Now, it does not guarantee a win, and skill can make up for it.
Size does not give a significant better chin because it doesn’t take much force to move the chin with a bare fist. However, every once in a while you will encounter a giant that has some skill and athleticism. If the person is much bigger than you, stronger, more skilled, and with similar athleticism, its time to run away.