I talked my chiropractor into taking his family on a cross-country train trip. Five of them traveled on the Empire Builder from Seattle to Chicago in a Family Bedroom and an adjacent Roomette. Obviously, a DC would be sensitive to such things, and he did not like sleeping in the Family Bedroom perpendicular to the direction of travel. He used an analogy I have read here before: that sleeping parallel to the direction of travel is the same motion as being rocked in a cradle, whereas sleeping in the other orientation is an awkward motion.
In my earlier post, I mentioned traveling in a mix of Roomettes and Bedrooms on an upcoming trip. I subsequently upgraded myself to all Bedrooms for that trip, and additionally selected Bedroom A. I have never felt that sleeping perpendicular to the direction of travel was uncomfortable. The only real advantage I see of a Roomette over a Bedroom is that it's better viewing scenery from the bed configuration in a Roomette because one can be looking forward out the window instead of sideways (as is from a Bedroom window--although I really enjoyed staying in bed all one day crossing Montana in a nice wide bed in my Bedroom in January). Also, in specific reference to room A versus other Bedrooms: being solo on that trip, I did not mind the sacrificed extra floor space, and I appreciated not hearing toilet noise or conversations from the adjoining room. When I travel with my wife, we're usually chatting anyway so I don't mind hearing personal noises from next door, and it's nice to have extra space by the chair when traveling with another person.