Me, I prefer the 15" (60') scale-girth cars, even if the prototypes were actually longer than 60'. There were 60' real cars, of course.
Why? In the "real" world of my "fake" world (the layout), even my 072 version, the 15" cars look impressive and accurate, except for the length, and on corners they look better than the 18" and especially the 21" versions.
I have a beautiful set of K-line 21" aluminum, ATSF cars - but as time has gone by, I often wish that I had gotten the 15" versions, which K-line also offered, I believe.
So, the new long cars are not on my list; in fact, if I ever see a set of K-line ATSF 15" aluminum cars, I might spring for them and sell the 21" versions. Maybe.
