Once you're on the ninja-path of dual-wielding, you have to advance your thinking past the point of "reloads."
Your hands are full. Of guns. There's so much shooting going on, that you NEED a gun in each hand. That means you don't have time to have one gun go dry, put the other (USEFUL) gun away in a holster, eject the empty mag in the dry gun, use your free hand to draw a spare magazine, insert and rack, then re-engage with the reloaded gun while re-drawing the holstered gun.
Theoretically, you could drop the magazine on the empty gun, re-holster (while still shooting with the good gun), insert a spare mag into the holstered gun via an administrative reload, re-draw the pistol and snag the rear sights on your belt or something else to cycle the slide... but that's dicey.
That takes 2 guns out of the fight.
If you're seriously thinking about 2-gunning, then you need to look at the insane capacity offerings (to avoid running dry). The fancy competition magazines that hold 20+ rounds, or the G17/G18 30rd SMG magazine. But not the Pro-Mag shyte.
Then, you've got to have more than just 2 pistols on the belt. New York reloads keep the good guns in the fight. You can either re-holster the empty gun or just drop it ('spensive, but faster).
I don't think I've heard of a "good guy" using a two gun tactic anywhere other than a movie, though. All that comes to mind is the Fort Hood shooter, the VA Tech shooter, and Columbine.