The Landmark is HL top of the line as you mentioned. Read recently tho that it may be taking a Siesta--dunno. Next is Big Horn and it's sibling Big Horn Traveller. Then rounding out things is Big Country. There are some features and floorpans unique to the BH and BC lines. From our experience, you have to do a side by side spreadsheet to see what's std/opt on each. We bought our BC in '17 as a '18 model and really only added 4-5 things as it was pretty well equipped for our needs. Did have a issue 1st year or so, but overall, been very happy w/ quality and workmanship. Unit is rated for full time use which may help in the quality of it AND it's not a light unit either. Quite sometime ago, was once told that a heavier unit helps w/ the ride of the coach and the reduced movement of things inside of it. I'd say that one is true.
Montana is always trying to come up/out w/ something new each year. Then it seems others follow. Plus, I want to say as well that the Monty's seem to be avail all over the place compared to HL units. This year from what I've observed here in CNY, the vast majority of coaches have been Grand Design units, Decent number of Cougars too. Alliance units have been seen a a fair amount as well. Hardly any Monty's, BH or BC's. No Landmarks. In fact, don't even know who handles the BH/BC brands in the CNY area now. Well at least the BC line. Hate to say it, but seen new BH's at Gander RV.
May not answer your question OP, but find a floorpan you like within each line you like, print off the specs and then compare.
