I recently switched back to black powder from modern powder and I was amazed that it was so easy to clean up. I use it in a cartridge rifle and after the shooting session I simply poured 4 cups of water down the barrel and dried it and it was squeaky clean. 30 seconds to clean. No 132.00 per gallon Hoppes, just cold tap water. What a pleasure.
I am experimenting with .45-70 loads now that use filler and if what I am hearing is true, the filler will go a long way to keeping the barrel unfouled. I may go to a .45-90 later on and use the additional room for filler and a nice plug of lube.
You are right catridge arms are easer to clean then muzzle loaders.
I still shoot smokeless loads in my 45-70s.
I been using tripple 7 in my non smokeless muzzle loades cleans very easy to.