Since riding is your main focus I would suggest two things. If you want a first class experience on the D&S ride the Knight Sky, which has modern comfortable seats with two on one side of the aisle and 1 on the left side. My wife and I rode in 2014 and she had to sit ahead of me on the single side, which was fine. This is a glass topped car with heat, and nice big platforms at either end for viewing. The downside is that its near the end of the train. It was on the 8 am train in September. If you prefer to be closer to the engine then go for an open car which I believe has side facing bench seating. Dress warm though cause it could get cold in the late fall.
On the C&TS if you want the first class go for the Parlour Car, or Tourist car. The Parlor car is on the rear of the train, and has several extras. Unlike the D&S on the C&TS you can move between cars, and there is an open gondola where folks congregate to listen to the docent and enjoy the open air with unobstructed views. Everyone on the train can use this open gondola. If you don't want to pay for premium service on the C&TS we like to ride in the first car behind the engine. Otherwise any coach is fine. Would suggest riding from Antonito to Chama, and. request seats on the left side of the train.
If you have never ridden these two railroads, they will surely be the highlight of your trip. Try to spend a little extra time at each place and see the trains and engines in action for a different perspective.
Good luck!
Greg
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