I do know that round nose FMJ's cannot penetrate sometimes. If they hit a bone at an angle, maybe, a windshield at an angle they CAN glance.
A bullet, to my way of thinking, has need to deform to some degree in order to bite or penetrate.
I think that penetration will cause more stopping damage than anything.
HP's can fill up with clothing or flesh and not expand.
A fast moving FMJ can penetrate thru and thru and not hit a vital organ.
A slow moving, soft nosed bullet can hit a bone and stop--doing damage but not penetrate.
I am a great believer in shot placement--in the heat, we often will not get the shot placement we want due to movement, external clothing, or angle and then be left with makeing sure we hit and not miss---that is often, in a matter of seconds/one or two or three seconds, all we have.
Luck plays a part--circumstances--angles--just a lot of stuff we have no control over.
Now i do favor a bullet that will deform and feel that it has a better chance of doing damage and carrying over the speed and impact of the bullet better than FMJ's.
Blessings