You never know in advance exactly what the fight will be or how it will go. If the issue is decided within the first few shots, and if you have not been taken by surprise...if...if..if...then three to five shots is often enough. On the other hand, if it is not decided within those first few shots, "firepower" becomes more and more important. That firepower may be found in spare mags, speedloaders, or a second...or even third...pistol. For those who might point out that a pistol is not "firepower", I will say...Maybe not, but if your pistol is empty, and mine still loaded and firing, then you no longer HAVE a gun!

For those who might point out that a pistol is not "firepower", I will say...Maybe not, but if your pistol is empty, and mine still loaded and firing, then you no longer HAVE a gun!

WORD !.....

It really comes down to carry ability and shoot ability. Many will choose a lower cap 1911 because they can shoot it better than a hi-cap glock or beretta.  
I will often choose a 38 snubby or NAA 32 because 5 or 6 rounds(plus at least on reload) with me is better than 21 at home(I shoot USPSA Limited with a Glock 35).
Now the person who picks the 1911 could opt for a hicap Para or STI but I have carried a full size Para and it gets bigger and heavier as the day goes.  Now I am speaking from a civilian point of view.
From a LE point of view where more danger is involved and you can carry in an outside the waistband holster which usually allows more comfort and stability I would go hicap all the way.

Is mag capacity important to me? Heck yeah. The idea behind packing a weapon is to:

1. Carry one that goes bang all the time
2. Carry one that hits what you aim it at
3. Carry one that knocks down what you hit
4. Carry one that packs as much ammo as possible
5. Carry TWO!

My main carry guns are a Beretta 92FS and a Walther P99. Both have pre-ban hicap mags with 15 round capacities. I carry at least 2 extra mags, usually 3. I also pack a Smith 442 as a backup with an extra speed-loader or Bianchi strip.

I am confident in the ability of the Speer 124 grain gold-dot +P ammo I pack, and in my ability to put those rounds where it counts. The Smith is there to make sure I can keep throwing lead if my primary runs out of ammo or pukes.