Just for information sake...
the bears that killed the cosby woman were put down by park rangers who used their 40 cal service weapons. I would suppose that a 12 guage with rifled slugs would be preferable, but then again this is theory because the current legal climate forbids the posession or use of firearms within park bounderies.
Having used pepper spray a time or two, one key thought to remember is to not empty the can while a bear is too far away for it to affect it. My use of the spray has been for defense against dogs when riding my bike. I recall one occasion in which I was riding at nioght and could not see the dog chasing me. I could hear him clsoing in and literaly felt his breath on my hand that was extended with the spray in it. At that point I sprayed him, and he immediately retreated. The next day I rode by and saw that the dog involved was a huge Chow. He started after me again only to turn and run away once he spotted the can in my hand again.
I don't suggest waiting until a bear gets that close, but I do suggest that you do your best not to panic and empty the can before it comes into range.
"Fly-fishing has many attributes, but none more pleasing than it's ability to liberate the young boy that still hides within me and to let that boy live again without embarrassment or regret, sorrow or anguish." Harry Middleton