Those pretty perfectly expanded bullets in the picture are what happens in ballistic gel. Problem solving in the real world is not done in ballistic gel. Therefore, while a 9mm may expand, a 45 certainly won’t get smaller....
And yes, .451 -.355=.086” in greater diameter, but last I checked, area is a function of r squared and pi, so .096” IS a bigger deal than simple diameter shows.
9mm area is .0989 sq in, 45 is .1597 sq in, or a 45 is 162% larger in area than a 9mm.
All said, indeed a hit with a 9 is much more effective than a miss with a 4, Finally, if a 45 is so much gun that you cannot shoot it well, then so is a 9mm. A 45 produces about 350 ft lbs of energy ( the same amount deliver to the target as delivered to the shooters hand) while the 9mm produces about 310 ft lbs. Not so much difference, espc in that most 9mm are much lighter, read greater free recoil) than a heavier 45....
Solution- use what you like, practice a lot with that choice.
Yep. The difference between an 8 inch pizza and a 12 inch pizza isn't "4 inches."