I'm a believer in 45 ACP FMJ for defense
First of all I'm talking about the 45 ACP at this is the caliber I personalty prefer. After looking at, trying, shooting many different bullet types I've settled on the The 230-grain bullet fired at around 850 fps FMJ for my 45. This is for several reasons. I do know there are many types or hollow points that have (supposedly) more stopping power and make a bigger hole at some point in their penetration, if all goes perfect. But here are my reasons, good or bad they work for me.
A. The 1911 was and is designed for this round all others have to in some way copy the physical requirements to function. (same reason that I carry a full 5" 1911. Shorter barrels are usually a compromise in reliability. Not always I'm told but I'm yet to be convinced.)
B. I like big bullets but like less velocity. Give me the feeling of the best threat factor and adequate penetration with less risk of a thru and thru shot that continues on to a secondary target.
C. Living in the cold country half the time people are wearing very thick winter coats. FMJ rounds penetrate this type of clothing more reliably.
D. Less expensive. I can practice with what I carry without a bank loan for ammunition. And everybody carries it in stock.
I suppose if I was carrying a 38 SP or 9 MM I might feel differently, or not. Not sure about that.