It seems that pistols are no longer available for wilderness ATCs, thus it is a "revolver only" game; so unless you plan to carry a Ruger Blackhawk Convertable or a Security Six in 9mm, a .357 magnum is more likely to be your weapon of choice in a .36 bore. I would like to say that the CFO's decision a couple of years ago to limit the authorization for wilderness carry to revolvers is poorly conceived and irrational.
As to the suitability of a 9mm for protection from wildlife, I'll come at this from a slightly different direction than some of the other posters. I think the 9mm can work, and here's why. If you need to shoot a bear with your pistol or revolver it is very close range problem, probably almost contact close. One does not open hostilities with a dangerous animal at long range with a handgun. The handgun is a last ditch weapon and is only used when you have nothing to loose. At very close range the bullet is at it's greatest velocity and will produce the deepest wound channel. The part of the bear that is closest to the shooter is the head, and it is the head that is the target. Aim at the head behind the eyes and ahead of the ears, within the width of the snout. While not requiring master marksmanship, the target will be in motion, and due to the circumstances the shot is demanding and can only be pulled off by a very cool hand. The target weight, that is the weight of the bear's head rather than it's total body weight, even on a very big bear, will not exceed 200 pounds. Even those of us who dislike the 9mm must concede that it is capable of good penetration on a 200 pound target.
The cranial cavity does not respond well to high velocity projectiles, and the results of a gun shot wound from even a low powered cartridge typically chambered in a service pistol will produce an immediate effect, provided the bullet enters the cranial cavity, unlike a center of mass shot on a 200 pound man. This is a marksmanship problem not a ballistic problem because the bear's head is deceivingly wide while the cranial cavity is narrow. And here comes the part that can make the pistol attractive in the bear defense roll. Recoil from the pistol is light and follow up shots can be fired quickly, something that cannot be said for a magnum revolver. Shoot at a bear's head with a .475 Linebaugh and miss the brain pan and he may be on you before you can recover for a second shot. Miss the brain pan with a 9mm and with luck you will hit it with a fast followup shot.
Now I'm not about to trade in my .44 for a 9mm but I also have a .357 on my ATC, and truth be told, there probably is little practical difference between the wound volume of the .357 and a 9mm when the target is an enclosed vessel like the brain.