I started off learning how to shoot a handgun with the Weaver stance, both versions with the shooting arm straight as well as bent. It worked and I shot well with it.
I then started leaning towards techniques that were oriented closer to what a person does in a "startle response" or "fight-or-flight response," namely Isoceles.
One thing that turned me towards more of an Isoceles stance was reading an article about law enforcement training where a majority of officers trained in the Weaver stance reverted to Isoceles when in a stress shooting. I wish I could cite that source.
Another reason is that I'm cross-dominant (right-hand, left-eye), so Isoceles works better than Weaver for me in that regard.
I also seem to get a better "body index," for lack of a better term, when it comes to getting quick hits on target at close range using target focus rather than sights focus (i.e., not quite point-shooting, but not exactly sighted-shooting, either).
So I would say I mostly use Isoceles. It may sound "tacticool," but I actually like the idea of a shooting "platform" as opposed to a "stance," with the idea that defensive shooting should be focused from the waist up in order to better respond to different situations. "Stance" always makes me think of being "rooted."
I do think people should at least be familiar with different shooting techniques, but ultimately it's up to each individual to figure out what works best for them. As long as they can get good hits on target it doesn't really matter as far as I'm concerned.
Of course, I hope it goes without saying, that defensive-shooting oriented people should also be practicing one-handed shooting.
Oh, and I will add that when I'm doing slower, more precise longer distance shooting, say past 10-15 yards, I do find Weaver to work better for me, despite having to turn my head practically 45-degrees to the right to line up my left-eye with my sights, kind of like Murtaugh from the "Lethal Weapon" movies. It feels more stable when I'm trying to make more deliberate, precisely aimed shots.