Bear spray is all the casual user will ever need. Anyone who fishes extensively in Alberta or BC is bound to have an encounter with a bear at some point, a knowledge of the behavior of bears is the best weapon you can ever have against an aggressive or antagonized bear, without it all the other tools are useless.
I agree that carrying around a rifle makes your #### longer and your beard more full and luscious, but bear spray is pretty awesome stuff. I'm shaking my head at the guy who said his crew leader bear sprayed him.
I would say spray is easier to operate than a rifle or shotgun, and the perception that it is some mist that will carried away by wind is pretty far from the reality which is more like spraying a "wasp bomb" aerosol on a grander scale.
When I worked in the field I not only carried around a ton of #### to which I would not be enthusiastic about adding a loaded shotgun, it was verboten by 2/3 companies I worked for to carry a firearm.
Working from a boat in NW BC? It's shotgun time...
I think 12 gauge is all about ammo availability, capability to single load for using the 3 step approach in camps (don't get me started on this) and ease of operation. For the guy who said "12 gauge with slugs is a rifle with bad sights" I would disagree totally. Beads are suggested for field carry because they do not get thrown off of adjustment, do not require lining up and provide all the front sight you need for an encounter occurring at spitting distance.
Most of the lit I've read on field technique from the past suggests "at least a .303 or a heavy shotgun", this stuff was all written before bearspray though.
I don't claim to have met a lot of bear guides but every one I have met carried a shotgun.
Ardent is it not acceptable to put bear spray in the side boxes of choppers? Do you fly a smaller one with the front storage compartment? I'm sorry I don't know their names. I have always hated loading them up and getting on them while they are moving though.
Well you've met another North Coast grizzly guide right here, who refuses to carry a shotgun.

I fly for the day job, but in fall I'm an outfitter on the North Coast BC, and we hunt grizzly. I've shot and seen enough bears shot with various guns and cartridges to have limited respect for the 12ga as a stopper, it doesn't matter the size of the hole it's just too slow. The wound tracts are also less impressive than a magnum rifle's.
We're a century and a bit behind what they discovered in Africa about the old BP Express rifles, heavy 4, 8, 12 bore rifles throwing large lumps of lead at shotgun velocities. As soon as the first nitro centerfire rounds hit the market they swept out the bore rifles, as they are simply more effective. The same stands true today.
As a utility gun, I like the 12ga a great deal, they are however inferior to even a standard rifle cartridge (ie. .303). Bears aren't hard to kill, even the biggest ones, being lightly constructed creatures with thin skin (in dangerous game terms, think bear construction vs a buffalo or rhino) and are very susceptible to shock from a bullet, the effect that makes them drop their head to their paws, lights out. You'll see that much less with chamberings that impact the animal under 2,200-2,400fps or so. Shot a lot of things culling (antelope admittedly) and was lucky to watch the effect of bullets run at different speeds and that's my personal suspicion, not science.
Flying depends on whether we have pods on or not, I don't always carry the pods and then everything has to be in the same air you're breathing in the cockpit. With the fixed wing I use for outfitting one has no external storage, one does. Either way I fly commercially to work as well and a gun and ammunition can be checked luggage, another benefit. The logistics for me simply mean the choices are ATC handgun or rifle, shotgun in a pinch but a last choice. Above anything I prefer the gun you don't put down or separate from your person, and spray also fails in this regard in aircraft even when it can be stored externally.