I too own a Glock 23 .40 S&W. Good choice for a CCW. So is the G-21 .45 and the .357 Sig. It's so true that a choice of caliber and firearm, depends on if you are bugging-out or not. Either way, becoming a competent shooter is important.

Regarding bugging out, there are different scenarios. If you are bugging out without a vehicle you need to pack light. My personal preferences would be for a .22 pistol, the Sig (Hammerli) Trailside is light, has a rail for a red-dot or other sight options, breaks down easily (that's a biggy) and is very accurate. Three hundred rounds of .22 weigh less than a box of 50 .40 S&W. So, for a game getter that must be carried on your person along with a BOB, I prefer .22 . For ammo, the CCI Velocitor ammo could easily take down a deer IF you placed the shot correctly (did I mention being a competent shooter is important?) and could be used for self defense as well.

For a true self defense gun? Well, I bought my daughter a 12g Remington 870 express smooth-bore, with extension tube, one in the pipe and 6 on board. The absolutely best double-ot ammo is the Hornady #8624 This ammo has the potential of placing all pellets in a silhouette at 35 yards (!) Unless you cloak such gun somehow, it would be pretty identifiable if carried while walking along with a bug-out bag.

For home security? A Remington 870 for everyone in the house. I also have an AR-15, great gun.... Other's I'm considering include the .40 Keltec that fits Glock mags and the 223 that takes AR mags....too cool.

Anyone who is a beginner handgunner, I would highly recommend getting into some sport type handgunning, like Bullseye. It will you help learn trigger control; IMHO this is the most important part of shooting a handgun. Plus shooting a fun sport. As you get better IDPA (International Defensive Pistol Association) shoots will help you understand tactics.
IDPA