When selecting a firearm that you will depend your life upon, there are four very important factors to consider:
Your gun must work each and every time you reach for it. This means your gun must be of good craftsmanship (you get what you pay for) and remember KISS – Keep It Simple Sister. Don’t go crazy with custom upgrades, except night sights.
EFFECTIVE STOPPING POWER
Your goal is to STOP someone who is actively trying to kill, cripple, or rape you. There is debate within the industry of the minimum caliber that you should carry as a primary defense gun, whether .380 or 9mm, which is a separate conversation. Regardless, you must consider the various barriers, such as seasonal clothing that needs to be penetrated and distances/accuracy.
You must be able to carry your gun open or concealed on your person throughout your daily routine. Select a gun that is the correct size and weight related to the size of your body frame and/or ability to carry extra weight. If you intend to purse carry as your primary option, adding a big ole gun to your already heavy bag is not really an appealing idea. This is a lifestyle choice and if your gun does not fit your wardrobe or body frame you are less likely to have it with you everyday. If you don’t have it with you when you need it, how can it help you?
The gun you choose to potentially save your life someday must make sense to you. It must be designed to use quickly and efficiently AND match your muscle memory. In other words, if you choose a gun with no external safeties your training should really emphasize trigger finger discipline when drawing from the holster. If you choose a gun with an external safety, then your training should include drawing from the holster and sweeping the safety. Safeties and other controls must be designed so you can operate them efficiently without having to modify your strong-hand grip.