Not trying to derail the thread, but even a powerful handgun has relatively low energy when compared to a shotgun or a rifle. If you are trying to kill a bear, big bore handguns will do the job nicely. If you are trying to stop a charge, you need to kill the bear NOW and not in 30 seconds, because a sprinting bear will cover the 50 yds between you in a little over 2 seconds, and those 28 seconds when the bear is gnawing on your skull will be the longest 10 seconds of your life. So, while I understand the attraction of a large bore handgun, if I were in big bear country and they posed a credible threat, I would carry a rifle or shotgun for backup.
Energy is meaningless and far too dependent on velocity, the most rapidly diminishing factor. If a 250gr .45 at 900fps will pass completely through any deer that walks yet only produces a paltry 450ft-lbs of energy, then something should tell us that maybe energy is not the proper gauge of a cartridge/load's effectiveness. The only disadvantage of one of these heavy sixguns is that they are more difficult to hit with than a shoulder-fired arm. A heavy hardcast bullet with a sectional density of .250-.270 will break a shoulder on its way in and break a hip on its way out and anchor a charging bruin as quickly as any rifle.
Shotgun slugs have a pitiful sectional density but a heavy rifle is a superior stopper because it is quicker and easier to place an accurate shot. The problem arises when you're doing things that cannot be done with a rifle in your hands or slung on your shoulder. The heavy sixgun is with you ALWAYS and that is its biggest advantage.