I work in the backcountry in Oregon, Washington, Northern Idaho or Alaska for days or weeks at a time and throughout all seasons of the year. Primarily mountains, then foothills or along river systems, and almost always away from trails. Usually with one other person, though sometimes with three to five other people operating out of field camps. Have had a few brown and black bear encounters over the years.
Weight is always an issue, despite 25+ years of professional military and backcountry experience, close study of what I do and don't need, as well as keeping up with performance gear. So I give a lot of consideration to pros and cons of every ounce and pound that I can. Always carry a day pack (usually 25-35L Osprey) with hip strap, or sometimes larger packs if carrying large GPS manpacks, remote sensing gear, camera or other specialized equipment. When working in Alaska, we carry bear spray and issued Remington 870s with slugs, or have the choice to carry ported Weatherby .375 H&H Mags.
Down here, I used to just carry bear spray, but had a particularly close call with a bear a few years ago that made me regret not carrying a firearm that day. Have tried lots of options since, but for the last few years have carried and loved a Gen 4 Glock 20 with Underwood 220gr. hard cast for bear country, or Hornady Custom factory XTP in 180gr. if I am more likely to run into lighter or two-legged trouble. Both rounds are like laser beams in my particular G20 fitted with yellow Trijicon HDs.
The G20 and all of my other backcountry handguns ride in Simply Rugged Sourdough pancake holsters usually strong side IWB with a Wilderness Instructor's belt, which works fine with the Osprey daypacks. If riding on ATVs a lot, will sometimes carry cross draw, but rarely. If wearing Simms chest waders, I can add the Chesty Puller harness for chest carry. Rob added a removable retention strap for the 10mm rig that attaches by Chicago screw if in waders.
Since I have been using the 10mm, I haven't looked twice at my old standbys. The G20 stoked with 180 gr. XTP and IWB is also great for getting to and from the field and has the same manual of arms as my EDC G19, which is a plus. Of course, bear spray is always on my hip strap, and the 870 always comes along in the crew vehicles, ATV, or canoe and goes on the shoulder in dense bear areas or after sightings in areas that we are unable to move out of/avoid.