What I find is ironic is that some the same posters that said a BP revolver is inappropriate or shouldn't be considered have said elsewhere that their revolver is "100% reliable", "goes bang every time", "after tuning I would trust it with my life", etc.
First, you have to get one that you can shoot extensively. Then, you can decide if it's reliable. I have some that are tuned and they will fire every time I want them to. I'd bet money on it. Next, you have to figure out if it and you are accurate. If you can't hit anything with it, well why carry it. You'll need a good holster or way to carry it concealed if that's what you want to do.
In some jurisdictions, you can carry a BP revolver in places where a "modern firearm" would be prohibited. I'm not trying to be a lawyer or pretending to be, but for example the School Zone. Some laws prohibit a firearm within so many feet of a school. Unless there is some exemption in law, those driving through the School Zone with a modern concealed pistol are breaking the law, but the guy with the BP revolver may not be. Some other places may prohibit "firearms" but the State statute exempts BP revolvers as they are "antique firearms". Maybe you can't afford a modern gun or don't have access to a store to buy ammo, etc. For some reason you have a BP revolver. Well, use it. Lots of reasons that are unique to an individual and circumstances.
I have two BP revolvers that I carry a lot. One is a 1858 style "Ace" or short barrel. The 127 grain balls are going 975 FPS average. That is as much or more than many modern cartridges. Another is a 1851 Navy with a 3" barrel. It's a little trimmer and lighter, but mine doesn't have "safety" notches between chambers, so I load it 5-shot. Lastly, the NAA Super Companion is just a .22, but knowing how to load it can push the 30 grain conical 600 FPS and (I know its not recommended) pretty close to 1000 FPS. That's a tiny 5-shot that you could stick in a shirt pocket.
I make it a point to go to the range about 4X per year. I will shoot some of the BP handguns each time, so that all of them are shot 2X per year. They are loaded otherwise. Some are in the house, one in the truck and some I carry. I have yet to have one not go off on a range trip or when I cocked the hammer and pulled the trigger.
I've not had to do this yet, but I know someone who does once in a while. If the gun is exposed to any moisture, weather related or some other incident, he pulls the caps and puts the cylinder in a food dehydrator overnight. Any moisture is gone, the powder is dry as can be. Make sure the temperature is low and use all due caution. I am not saying its a great idea, but it has been done and worked so just be careful if considering it. Put fresh caps back on it in the morning. I know he did this twice and we purposely went to the range within a few days afterward. The guns fired just fine.
There's a lot of folks saying there are better choices and I agree. Sometimes you don't have those choices. A new small car will get better gas mileage and save you money while being reliable. Your old carburated pickup is touchy and a gas hog but you own it and can't afford a new car so you make it work and keep going. Same premise. Don't carrry a BP handgun to be "cool" or make some kind of statement, and if you are truly exposed to danger don't take a chance you don't have to. But if you need to and work to be confident in reliability and accuracy, go ahead.
I will take my handgun that's been loaded for 6 months or longer, dunk it in this 5-gallon bucket of water for a second and shoot at whomever volunteers to stand down range. Nobody will volunteer........