I'll try to go back to the OP's question WRT a "carry" gun and a "combat" gun. While I agree that risk assessment and mitigation are the best tools in the toolbox of any armed person (LEO, military or private citizen), the truth is, kitten happens. And kitten happens when you least expect or want it to. If we could predict when/where our Gun Fight was going to happen, we either wouldn't be there, or we'd be there in full kit, with belt-fed automatic weapon support, and a squad (or at least a fireteam) worth of hand-picked team mates.
I can't get into specifics, but I recently had the opportunity to talk at length with a number of guys who were involved in an Active Shooter response. I know all of them fair-to-middlin' well, and three of the five of them are, literally, guys I'd hand-pick from my agency to be with me if I thought I was going to my gun fight. EVERY SINGLE ONE OF THEM was SIGNIFICANTLY kittened up, equipment wise, when the "go" light went off and they had to dance with the one that brung them. Two of them, because they were going to the range that day, had their "backup" guns on them with no spare magazines - they're "primary" pistols and all their magazines being left behind in their range bags either at the office, or in the car on-scene when they went to work. I could go on and on and on - and these are good, switched on, tactically minded guys.
The moral of the story is this. If you think your threat assessment skills are so good that you can "get by" with a carry gun only, you shouldn't need a gun at all, being able to avoid trouble in advance. If you need a gun, you need a REAL GUN, and, to some extent, capacity matters. Even more so, SHOOTABILITY matters. I know I can shoot a 298 or 300 with my PM9 when I work at it, but, if I need to shoot an El Prez, or a Bill Drill, that's NOT the pistol I want to use.
Now, I know there are compromises that we all make. Now that I live up North, it's a LOT easier to conceal a G19 and G26 with spare magazines on a daily basis, even in the summer. I know that there are lots of private citizens for whom the decision is a deep concealment gun or nothing, based on employment policies and what-not, but that's not what I'm addressing. What gets my goat is the idea that you can "get away" with just carrying a "little" gun, because you're going somewhere "safe." NOWHERE is safe. Not your Church, not your office, not the movie theater. When the monster(s) come through the door, I guarantee you will not, afterwards, say: "Gee, I wish I had a smaller pistol with less ammunition during that fight..."
As always, this is one man's opinion, and worth precisely what you paid for it.
Regards,
Kevin