Even a individual who are well trained in using a firearm will still be at same odd of getting shot as the shooter themselves. What help is they may be a bit better at using the firearm, but that is easy to say until adrenaline hit them and their life are on line.
So in end it is still 50-50 chance for both side. If someone want to be able to use their firearm, they have to understand that firearm is just a tool and what make them effective is how they use it.
For example why would you just stand and try to shoot the person who is doing same as you? Why not try run and hide then catch the person from behind by surprise or something? That's call tactic. Tactic is what help.
When it come to most people they just have no idea what they'd do they just think they would pull gun out and shoot the shooter dead and thats it. Not exactly a very effective method.
BTW I think anti gun crowds are bunch of idiots because they act like as if guns are banned, it will stop everything when in fact a very determined person would simply turn to bomb, poison or other means. But I am just starting to leans toward them simply because it seems like most gun people are just a plain idiot who think shooting somebody is like playing a video game which doesn't make anything safer.