My opinion only...
But if it happens that you have to reckon with more than one adversary (and don't count on them returning fire with a "spray and pray style"-not all crooks are cowardly and stupid), you might be better armed having a high-capacity, reliable semi-auto in your hand with a spare magazine at your disposal.
You know what? I see this argument all the time, and on the surface it makes sense.
On further thought, though...if I am 1v2 or 1v3 (or worse)...and all of them are armed and returning fire (and that is assuming I get the first shot) then I believe that I am in a world of hurt. In the movies, BruceWillisTomCruisepickyourfavorite may be able to gun down three bad guys without taking a hit. Can you or I? Probably not.
In other words, I think that magazine capacity will be the least of my worries. If there are three people shooting at me, it will be over before I have a chance to worry about reloading...and I will probably not be happy with the outcome.
In your post, you talk about aimed fire. If you have three guys shooting at you...you had best have some serious presence of mind, ice water in your veins and the luck o'the Irish on your side...otherwise you will have some new orifices very quickly.
In case I am not being clear...I am perfectly happy with a single stack semi or a revolver. If the worst ever happens, I hope I have some presence of mind (and the luck o'the Irish wouldn't hurt) but I also believe I have a realistic outlook.
Many people do not want to face up to the fact that there are certain factors that will not be within your control. I would rather have a (low capacity) handgun that I shoot well...and has a reasonable amount of power...than a large number of rounds that I may never use (or, worse, lend a false sense of security).
Cops have to return fire and conclude a fight. You and I have another option--if we are not hit in the initial volley, we may retreat (and should, at all possible speed).
The bad guys know this, too. They will continue a firefight with a cop, because the cop will either kill him or arrest him. Unless the BG has something personal against you, the initial confrontation/exchange may be enough that you will both disengage. He doesn't need to kill you to keep from going to jail; you don't have to pursue him.