I shoot too many calibers. I like to mix it up and shoot what ever when the mood hits. I know it holds me back from getting any better at stage times.
I like to shoot C&B a lot and that would be 44 or 45 cal balls depending on which irons. I shoot conversions too and they are 45 and I shoot cartridge with 38 spec brass.
It isn't a recoil thing with me, I shoot double duelist and am getting better at gunfighter, but I did start the game with 357 Cimmarons and shot the 38spec brass for economy. It was a good starting point, since I had the dies to reload with already.
Rifle I usually always shoot 38 spec with Snakebites. I always shoot a 12ga shotgun.
I do shoot only BP and I can get plenty of smoke from all my stuff.
I shag a lot of brass on my posses and I think the 38/357 from rifle would be by far the most popular caliber in my area from my observation. 12ga for shotgun.
Observation: I see more of the folks shooting 32/20 lately. I see less of the 44-40.