I've never really had a dog in this age-old fight, I like them both, and wouldn't feel under-armed with either.
I currently don't own anything in .45 or even .40, though I do still have a few hundred rounds of ammo (as is my habit) in case one of them falls my way again, which is quite possible given my wheeling-n-dealing habits.
But, in my opinion and experience, the majority of the arguments for the .45 seem to be largely based on things like nostaligia and personal preference, like this comment posted above: "9mm just doesn't thrill me to shoot as much as 45 and never will. Theres nothing like a 1911 loaded with 45ACP!!! "
That's all well and good, but it doesn't make the .45 "better", yet it always seems to comprise a VERRY large portion of the pro .45 arguments.
These days, I've come prefer the 9mm myself, and think it's more practical in some ways, and pretty much, just as lethal, round-to-round. Being cheaper,lighter and often eaier to find, is another plus.
I also think a quality pistol, loaded with a quality 9mm JHP, like Gold Dots, Golden sabres,etc, holding 15-17 rounds, is a significantly more lethal and effective weapon than any .45 holding 7-8 rounds. I don't think this is rationally disputable.
And please, spare me the predictable diatribes about "shot placement". If any of us are carrying the groceries out to the car, and 3 bad-guys pop-up outa nowhere, almost no one here is going to be cool and calm enough to land 3 quick head/heart-shots like Clint Eastwood. Even police officers that live on the mental edge every day, when surprised by a bad-guy, very often go right into the "spray-and-pray" mode, tossing rounds all over the place, and we've all seen countless dashboard cams showing exactly this. It's the REALITY.
The undeniable fact of the matter is that the extra rounds in a modern 9mil offer a SIGNIFICANT tactical advantage over a revolver or 1911, one that in this day and age, is almost foollhardy to pass up.