What I've learned and what I like:
(1) The "best" handgun for self defense is the one you train with to become deadly accurate with at ranges from 10 to 30 feet away.
(2) The "best" handgun for self defense is the one you are going to carry.
(3) I prefer the Glock platform for SD, and here is why
- chamber a round and the Glock is "always on"
- no safety to remember to disengage or engage
- same trigger pull every single time
- Accurate and reliable
- higher capacity
I do not like SIGs due the lack of an external safety requiring you to use two trigger pulls moving from DA to SA. I do not like where SIG places the slide release. It causes me to adopt a grip that is not intuitive for me. I have to keep my right thumb out of the way and put it on my hand, instead of on the pistol.
If I use a DA/SA pistol, I prefer those with external safety that allows me to carry "cocked and locked" (HK and FN come to mind).
I like my Berettas, but the safety operation is opposite of every other handgun I use, "safety goes down to engage it, safety goes up to disengage."
It really comes down to what you finally find works BEST for YOU.
So, try as many handguns out as you can.