DOK,
I'll start trying to answer your question by explaining that I have don't have a good answer, at least not vast experience. I've seen a couple of bears hit with handguns and have not been real impressed. Now, that does not mean anything and I am no expert by any stretch of the imagination. I have seen a bear hit with a 454 that was loaded really stout. I wasn't my gun and it was a few years ago but remember the guy calling them "proof" loads. His primers were really starting to flatten out. I can't remember exactly but think he was using 350 grain hardcast bullets. He did turn the bear (it had already been hit by a 44 with no visible effect) and after the bear was killed with a 375 H&H, we found that it did break bone and penetrate pretty good. Not quite the result the user was hoping to see, but then again turning a charging bear and escaping a mauling is a good thing on any given day as long as the bear is dispatched. The only bear I've seen hit with the 475 was a tad bit smaller and results were impressive. The bear still had to be finished but the 475 did stop it. But the bear was smaller to fair about it, still not small, but nearly an 8 footer. I have not seen a bear hit with the 500 and hope I never do (because if that happens, it will likely be because I had to pull the trigger). I am comforted in the extra weight of the bullet and penetration tests I've seen so far though. With the test medium being equal (a waterlogged spruce log), I've seen the 500 penetrate as well as the 454 and 475 and do it with a bigger bullet. These were informal tests and nothing that I've seen published. I don't have any conclusive results and don't recommend one over the other as I had no part in the loads or anything else. I may be wrong all the way around and the next post by a 44 user may prove just that. Just seemed to me the 500 was more destructive and powerful. There are just so many different variables that may make them equal, maybe if you slow the 454 or 475 down a little or used a different bullet design the results might change. The numbers may not show this, I don't know. I don't trust KE or Taylor KO's, or Keith's formulas. Shooting a wet spruce log with the heaviest loads we had available the 500 did more damage. That was what made me the most comfortable. That does not mean the 454, 45 LC, 475, 44 isn't good enough for bear. I don't mean to imply anything. I just feel more comfortable with the 500. That is my personal feeling, nothing more, nothing less. I know Bowen and Linebaugh both recommend the 475, I know several folks have taken the biggest bears with 44's and Keith probably killed a whole passle of big animals with 45 LC and 44 Special with remarkable results. I know also that all of these have been used in Africa with great results. My choice without taking anything away from any other cartridge was the 500. I don't have any real data to back up my choice, but it is truly terrifying to face a charging bear and I want what I'm most comfortable with. I may be and could very well be wrong. My loads for the 500 are really close to Buffalo Bore's loads. Not as hot as some folks I know that shoot the 500's but using the wet spruce log test, I get better penetration. I'm really new at loading the 500 and am not all together comfortable with my recipes and have no way of knowing what kind of pressures I'm generating, so I prefer to keep that to myself. However Buffalo loads do nearly the same thing, but that gets expensive when you shoot a lot.
I think it is also important to point out that there is not a bear behind every tree. Of all the time that I spend in the really remote backcountry up here I've had very very few encounters with aggressive bears. Probability will work out to be nil. If you used that for your null hypothesis, it would be rejected with full confidence. I know folks up here that have spent their entire life in the back of the beyond and never even carry a gun unless they are meat hunting.
Shooting big bore handguns to me is just not fun when you compare to shooting 38's or 22's. It's painful and I'm not as accurate. They are a part of my personal field gear for work and recreation, but that's because those activities take me to places I probably shouldn't be (as referenced by the fact that I never see anyone else when I'm there). If I lived in anywhere but here or enjoyed doing other things, I'd be perfectly content not to carry a sidearm or to carry a 357, a 22 or a 38. That 32 H&R in a Ruger single six or Vaquero (Bowen can put adjustable sights on the vaquero, by the way) sounds like the most interesting, fun and pleasant handgun I've heard of in a long long time. I really hope we can get more discussion about these class of handguns. The big bores are a specialized tool that is not much fun for recreational handgunning in my opinion. Hooray for the 32. I might just have to grab one of these myself when I save enough pennies. For shooting at the range, a pot gun or just a knocking around in the woods gun, it really sounds ideal.