I think is pretty much simply boils down to what do you like to shoot.
I have had a BP rifle for many years and never saw much point in having a BP handgun. That was because I was busy shooting cartridge based handguns. Then one day I realized how much I enjoyed the slower pace of shooting BP rifles. I didn’t have to pick up empty brass to reload, didn’t have to inventory multiple smokeless powders, buy reloading dies, order bullets, etc. At some point I thought that a BP handgun would be enjoyable to shoot so I now have three that I bought this year. I enjoy them as much or more than any of the modern cartridge handguns I have.
My point in this ramble is that most people’s tastes change over time and with increased age. I no longer enjoy shooting magnum loads out of my magnums, nor do I feel a need to hand load cartridges to their max SAAMI ratings. What I enjoy now is loading just to the point to effectively get the job done, which most of the time is well below maximum loadings, even in my BP guns I have found this to be true.
I am even enjoying what I have found to be the cultivated art of cleaning BP guns. What used to be something I saw as a chore I now see as an enjoyable part of the process.
So to answer your question, if you are anything like me, you will not be content for long with only one BP gun.
But, if you are asking what type BP gun you should buy first, I would have to say a rifle. They are much more flexible and useful than a handgun, IMHO. Also, they are much more accurate.
RAMBLE MODE = OFF :yakyak: