I posted a link up in reply #7 that accounted for all bear attacks from 1889 to 2009 where gun were used. There were 444 people, 357 bears (black, brown, and polar), and 269 close encounters with bear. Bears inflicted injuries in 151 of the encounters, and killed 17 people.
Aggressive bears were deterred or killed 84% of the time with handguns, and 76% of the time with long guns. People with and without firearms suffered the same rates of injury.
Between 1985 (when sprays first started appearing) and 2006 there were 83 close encounters involving 156 people. In all the incidents involving spray, there were 3 people injured, and none killed. They deterred attacks a bit more than 98% of the time.
You gotta make your decision, but if the choice for me came down to hitting a bear in the head while its running at me 30mph, with the target bobbing left and right, I think I'd take the cloud of spray for him to run through.
If you've ever had pepper spray or CS in your face, you'd know how unpleasant it is. If you think about a bears much more sensitive sense of smell, it's probably that much more unpleasant for them. It works for skunks, it'll work for you.
Bears go the other way when you blind them, just like people and everything else.
https://www.youtube.com/watch?v=CWnACum4SJsPit bulls don't care for it either.
https://www.youtube.com/watch?v=jsgvUohhpqc