I'm currently burning bituminous coal in my Clayton. I also can get very long burn times. It is not unusual for me to get 12 to 36 hour burns very easily. It is easy to burn, much like wood with long smolder time. With the proper draft settings, I get very little, if any, smoke coming out of the chimney. The things that I don't like about it is that it is very dirty, makes a lot of soot in the chimney, and each batch that I get has varied in quality.
I personally like to burn anthracite over bituminous coal. After this last batch of bituminous coal, I think that it may be my last time buying bituminous coal. The cost savings to me is not worth the added cleaning. Anthracite is so much nicer and so much cleaner to use for home heating.
Now after the wonderful experience of burning anthracite coal in a totally awesome, constant burning, highly efficient, easy to operate, appliance, the Coal Chubby, I doubt that I will go back to bituminous coal. I'm spoiled now and wish they made a furnace.
I now am a believer that the correct coal burning appliance for the type of coal that you plan to burn will make burning which ever coal you choose to burn either a pleasure or a pain, determine how much fuel you burn, and how much heat you receive from the fuel it was designed to burn.
So my conclusion is, spend the money for the appliance that you need to burn the fuel that you plan to burn. This will be a much more efficient and a pleasure to operate.