I think if you are someone with the makeup of the Dr in the video that started this thread then the answer would be YES, you would increase your survival odds or at least cut back on some of their survival odds. I would guess less so with the situations with the bank or convenience store. Hard to tell, really. I don't think anyone knows what they would do until it happens.
Still, for me, the BIGGEST advantage of having a partially armed society is the difficulty a would-be assailant(s) would have planning such an occurance with the concern or uncertainty that they might just run into an armed adversary. Who would ever be able to tell you how many situations have been stopped at the drawing board because the risk was too great? It's unproveable. Isn't it?