Hello Mike, Bitum. coal is often higher BTU content that Anthracite. HOWEVER, the BTU content is based on burning all the volitiles in the coal as it first starts burning. For you and I this means you must have a stove/furnace/boiler that is designed to burn Bitum. coal, and has a fan-forced preheated secondary air passageway to blow hot, oxygen-rich air into the flames to burn off the soot. Your Clayton doesn't have this I'm pretty sure. So you wo't be able to burn up the soot, so that is wasted BTUs. So the Bitum and Anthracite are pretty much equal in heat output
So the main difference between Bitum and Anthractite is just as you stated, the Anthracite you can pretty much just load onto the fire, close the door a walk away. The Bitum. you have to close the door to keep the soot from escaping, come back 30 minutes later to break up the stuck-together crust, and then keep an eye on it to see if the ash clinkers, clean out the clinkers and excess ash off the grate.
Bitum is a lot of work, but costs 1/4 to 1/3 the price of Anthracite.
What I did when I was still using both Bitum and Anthracite was to load on the Anthracite at night a deep load of coal to have a good hot fire all night long. During the day when I was home I'd burn the Bitum 'cause I could 'fuss' with the fire every hour or two.
Bituminous often has a much lower ash-fusion temperature, around 1200-1500* Anthracite is usually around 2700*. What this means to you and I is that the hot ash in the bottom of the firebox can be molten and ooze together and make sheets of stuck together ash, called clinkers. These sheet eventually stop up the grate and block the air to the fire. I used to have to let the fire burn out every week or so and clean out the firebox and grate. Anthracite doesn't have this problem unless you are burning it VERY hot.
Hope this answers your questions