I prefer Post War, MPC and PWC Lionel F3s for running. For display and just for looking at them I prefer the modern scale engines with prototypical paint jobs.
I like the almost timeless nature of the former type in that they seem OK with nearly any rolling stock. With modern scale engines for some reason I feel a need to fit them with rolling stock of the "right" time period, dimensions, road names, prototypical detail and so forth.
The older engines seem more at home with the less prototypical paint schemes or brighter colored or glossier looking cars and with cars that are all different names, rather than going in for an attempt to have many cars be the same road as the engine and that type of thing.
Then there's the matter of what I call "approach avoidance" to anything with finicky, delicate, hard and expensive to replace electronics.
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