I read one time, somewhere on the internet, that the best way to understand the lethality of a caliber is to understand the energy it creates.

I can't remember the formula, but it was explained that greater bullet mass creates more energy that can then be transferred once the bullet strikes an object. For example, a car and a baseball could be traveling at the same speed. But since a car has more mass, it transfers more energy when it hits an object, thus creating greater carnage.

I see and hear debates all the time about 9mm versus 40. versus .45. I understand that a bigger bullet makes a bigger hole, etc. Many people argue, however, that a proper 9mm hollowpoint can be nearly as effective as a .45. But haven't we forgot about the energy a bullet creates. Doesn't a .45 transfer more energy because it has more mass? And doesn't more energy mean more lethality?

Could someone tell me if all this is true or not? Also, why is this rarely brought up?