I have a Glock 17 for home defense pistol. With proper ammunition selection, the stop rate of a 9mm is within 1% plus/minus of a 45. Also, follow up shots with a 9mm are quicker/easier due to less recoil. Not to say a 45's recoil is going to kill you but it is noticeably greater. Glocks are like the Honda of the gun world. Not the prettiest, not the fastest but it always works. I can't even begin to tell you the things I have put mine through....Thousands of rounds later it's still ticking.
Shotguns are not necessarily the best options. A miss conception is that the buckshot will not over penetrate. I can tell you from personal experience that 00 buck will go through multiple layer of drywall/doors. Believe it or not with the correct ammo an AR15 is better regarding over penetration. They are also much more fun to accessorize
