Personally, after 50 years of backpacking, hunting, and working with bears professionally for 20 of those years (including one charge by a 400 lb black bear). I would NEVER recommend a 9mm for defense. If only smallish bears were to be encountered (say, 200-250 lbs max) and I HAD to carry 9mm, I would carry one of the Underwood penetrating loads. My personal experience with Buffalo Bore is that I have had too many mis-feeds to rely on it and accuracy is not the best (I agree that YMMV). I carry the hard-cast Underwoods in my 10mm in grizzly country or I carry a 45 Colt/454 Casull.
In my experience seeing bears running (either towards me or away from me!), you'll only have time for ONE defensive shot. Killing a grizzly with a 9mm was a fluke.