I don't think there is enough visual difference in the cars for the average public to care. I'll admit to searching out a car that I have seen railfanning because it was unique and stood out in a train. So many of these ACF cars look the same in a train that most people could care less about the differences that make them unique. One big covered hopper looks just as good as another to them. The IM cylindricals are unique and stand out, so they sell, the new 2600's are unique and not a normal sight in a train (at least around here) so they sell.
I watch the 40's and 50's railfan video's looking for cars to set the era and the thing I notice is lot's of box cars with varying roof heights, so that is what I look for to build a train. In a modern train, the covered hopper, tend to look the same in a train. You may notice the number of bays but most people don't even get to see what type of roof hatches it has from their vantage point. In a train, it's hard to pick one type out from another.