TL;DR - In the eyes of the law, no handgun is overkill.
Short of a "handgun" in a rifle caliber, the major handgun rounds cannon across the board promise a one shot stop. "Stopping power" has much more to do with shot placement, and the physical and mental state of the one being shot than any terminal ballistics of the round.
That being said, modern ammo in the major handgun calibers are so close in real performance that it truly comes down to shooter preference.
I like the 9mm cartridge because at least in my area, it's cheaper, which means I can practice more under a certain budget. It also allows for a larger capacity magazine, which is a benefit (in free states).
As far as manufacturers, as long as you stay away from Highpoint, you should be fine. A friend of mine has a Highpoint .45 and the thing malfunctions every time he takes it out.
Glock, S&W, Sig Sauer, Ruger, Kahr, Kimper, Colt, Taurus, etc…they all make fine handguns.Post too long. Click here to view the full text.