I have to agree with several other post......If I am personally attacked, I am going to fight, shoot and defend myself and/or family to the death.
However, as a non-LEO, and no desire to be a hero, if I witness an armed robbery, regardless of what weaponry they have, I would be reluctant to take action unless maybe they just had a knife, axe, or sword and I had a clear shot and a life was in danger. If I was in a mall or movie theater and a shooter showed up with an "assault" style rifle, am I going to attempt to "take them out"? I don't think so, especially if I just have a handgun (any handgun) and they have a rifle, with possibly many extra mags......and bent on killing as many people as possible.
There are just a few reasons for my rational.....first, if I take cover, have my weapon out and police/security arrive, they don't know who I am and chances are, I'll be shot by a good guy. Second, I would have a clear disadvantage with a handgun vs assault style rifle or a shot gun.
Third and finally, CIVIL LIABILITIES.......I may not get killed, and hailed a hero, but someone is going to sue me......the bad guy, the bad guys family or the ACLU. Additionally, some innocent bystander that may have been dramatized is going to sue, even though I was the "hero".
So, in closing, I sometimes CCW a Glock 32 (.357 Sig) with 2 extra magazines (26 extra rounds) or a J frame with no extra ammo....No rhyme or reason to the CCW rotation, but I do believe in the 3-3-3 rule. 3 shots in 3 seconds at 3 feet.
I try not to visit places where there is a chance that I will be attacked by a gang and if I do, than the Glock and 2 extra magazines are in order.