Most of the time a gun is used defensively (>90% depending on the study) it is not even fired.....
That's one of the more important points that people mis understand.
Sure, you don't want to focus on the "normal" or "expected' scenarios to the complete and total detriment of all of the possible fringe scenarios - but you also don't want to weigh yourself down in preparation for highly unlikely fringe scenarios to the detriment of what you will most likely encounter - especially when you can mitigate the potential for those fringe scenarios.
In other words, then 90-95% of defensive handgun uses don't even involve firing the handgun, it really doesn't matter what caliber it is or how many rounds are in the magazine. All it needs to convey to the assailant is "you're about to get shot" and in those 90-95% of situations it's going to be sufficient to stop the assault as the assailant flees.
Consequently, one of the most effective decisions on defensive handgun choice is to choose one that is convenient enough that you'll carry it all day, every day. That's 90-95 percent coverage for all of the scenarios where you might need to defend yourself with a handgun.
A better handgun, better cartridge, larger magazine or more magazines can all help improve your odds for that last 5-10%, where you might need to fire, but only a tiny fraction of those will actually need a duty sized handgun and multiple high capacity magazines.
And again, there is nothing wrong with choosing to carry all that. But you do have to be aware that there is a point of diminishing returns. Beyond that point the weight and bulk of the chosen EDC make it less likely you'll carry it all day everyday. The EDC becomes far less concealable, creating other issues in terms of telegraphing you are armed and limiting the situations where you can be armed without creating other issues. And if you ever do have to use it, it will raise questions with the police, the prosecutor, the grand jury and potentially the jury about why you felt the need to go to the Piggly Wiggly armed like you were expecting to participate in a gang war.
In other words, sometimes too much is too much and if your alternative in those situations is nothing at all, you not only lose the very minimal gains for those fringe scenarios but you also leave yourself at a disadvantage for the car more likely 90-95% scenarios.
There's a sweet spot and that sweet spot will be different for different people.