You dont have to be a gun expert to know what gun you would trust in a fight after youve fired a 45 and then a 9mm.
Well, I am something of a "gun expert".
And I carry a Browning High-Power 9mm.
I used to carry a 1911 .45, until it became very clear that 14 rds. of 9mm is far better than 7 rds. of .45 when facing multiple assailants.
I am a pretty fair shot, but having to shoot in the real world, where the bad guys are shooting at YOU, from cover, I realize that the extra rounds are more important then just "stopping power".
In reality shot PLACEMENT is far more important than caliber.
I know a man who survived being shot with a .50 BMG round, and of several others who have died from .17 pellet rifles.