Honestly, you buy a firearm for one of three reasons: 1. Need, 2. Aesthetics, 3. Hobby.
If you are purchasing for #1, it should be whatever you need it for. My standard carry arm is a Taurus 1911. It's .45 ACP which I am comfortable with and makes a good self-defense round, it's reliable, it's accurate, it fits my hand, and it's comfortable for me to carry year-round.
As a trainer in firearms safety and carry, I make suggestions. A firearm should be comfortable to the user and fit for the purpose you need it for. I've had some people I've trained get a .380 ACP small-frame, others I've suggested a .38 Special revolver. Some a .40 Smith and Wesson, others a .45 ACP.
If I have an opinion, it's that revolvers are very very well-suited to easy carry and good emergency self-defense. They are mechanically reliable, simple to use, and have decent accuracy at the short ranges of the average self-defense use. Semi-automatics (automatic implies it fires fully automatic) tend to be larger due to the larger ammunition capacity, require more training, and tend to be less reliable (though that is a factor of make, model, and maintenance in 90% of cases.) People who carry professionally for self-defense tend to use semi-autos, whereas those who carry for animal protection tend toward revolvers since they have larger calibers available.
/lecture off
