I model both the Baltimore & Ohio in the 1950's and CSX in the present. I have always been a fan of the B&O, loved those early EMD GP's. I also love the new stuff. So the only way to enjoy both is to model both.
As far as location goes, I have not completely figured that one out. I would love to model from Grafton, W.Va. to Cumberland, MD with helper pockets and the whole nine yards. But space, time and money may not permit that. I also have to have some element of switching. One without the other will not do.