Those pretty perfectly expanded bullets in eh picture are what happens in ballistic gel. Problemsolving in thereal world are done in ballistic gel. Therefore, while a 9mm may expand, a 45 certainly won’t et 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 ta a miss with a 4, Finally, if a 45 is so much gun that you cannot shoot it well, then so is a 99mm. 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 9 read greater free recoil) than a heavier 45....
Solution- use what you like, practice a lot with that choice.
“...a 45 is 162% larger in area than a 9mm”
WRONG