Back to the title:

I bet Gramin is thankful he was not carrying a .22 or .380.
Hitting the douche-bag in the vitals may not have stopped him as expected, but it likely slowed him down - as opposed to not being hit.
Shooting through a windshield with a small caliber would have been much less effective.

The Spec Ops guys chose the .45 over the 9mm for a variety of reasons.
Having a choice myself, I'll stick with the .45 for defensive carry.
Just Sayin.