I carry a .45. Actually having used a handgun to defend my life and been shot at a few times, and yes, hit, I have figured a few things for myself.
A) No one EVER said, "Gee, I wish I had a smaller caliber handgun!"
B) No one ever said, "Gee, I wish I had less ammo with me" or "Gee, I sure am glad I left that spare mag at home!"
C) Make that first shot count. If you miss, you are 1) down one round, 2) they are making for cover and you aren't getting any good/easy shots like the one you missed, or 3) THEY are standing there blazing away at YOU, and YOU are headed for cover and not getting any easy shots like the one you just blew.
D) If you can't end it with 8 rds, what makes you think you can with 15?
E) Don't worry about wearing clean underwear when you get up in the morning. Sure everyone else will appreciate it, but believe me, having some loon leaning through your car window with a loaded pistol and hitting you in the face as you turn, well, chances are good they won't stay clean long, and afterward no one will care if they are clean anyway. You might like to carry some baby wipes and clean underwear and pants in the trunk though. Everyone WILL appreciate that.
F) If a new superduper bullet in the 9mm makes it "equal" to the .45, why not get the same superduper bullet in .45 and shoot THAT?!
G) Shoot what YOU like and what YOU shoot well and to heck with everyone else! They can shoot what they like and shoot well and everyone goes home safe at night. As long as YOU are happy, piss on everyone else and their opinion.
H) Discussions like this are fun to kick around, but most generate a lot of heat and little light. In the end, see G above.