Easy answer, directly from Mr. Herter himself.... "The fabulous .401 Powermag...is the ideal large caliber revolver cartridge. Will kill any animal on the face of the earth, or shoot through the cylinder block of any automobile. It will flatten any human, no matter where you hit him...This is the finest big game or law enforcement revolver...With this revolver you can hunt deer, and all North American and African game...".
I have decided 9mm is fine for a myriad of reasons but first and foremost is that I can shoot it well, the guns I like are chambered in it, I can readily find ammo in 9mm, and it doesn't cost so much that it is prohibitively expensive to shoot it.
Although, when I go camping I usually bring my Smith and Wesson .357 magnum revolver.