Actually, I like the buck and boom of .44-40. Got a 73 and a pair of peacemakers in .44 WCF. .44-40 was my first SASS cartridge.
Then I fell in love with the 1872 open top. So now I mainly shoot an 1866 and open tops in .44 Russian. I shoot BP, so there is still plenty of boom and smoke. I suppose I could shoot them in .44 Special, but .44 Russian seemed more appropriate, even though the case volume on the .44 Special is actually closer to that of the .44 RF Henry.
I recently built a pair of 1851 conversions - Pietta 1851s with Kirst gated converters. I load 171 gr heeled bullets over a full case of FFFg - about 18gr. Never had a problem with any knock down. Based on published ballistic info, I suspect it has a muzzle velocity of about 700fps, giving a power factor of almost 120.
Point being, if you load BP, you have to work hard to get a gamer load. It takes filler or really light bullets.