I'll always be a Chessie fan for the prototypical things. So if I were actually modeling a prototypical era I'd do the late 80's when the Chessie/SCL/L&N merger was taking place to create CSX.
I picked the UP. They have a lot of history behind them, they run in my home state (HQ about 60 miles from me actually), and they ran some of the best steamers on the rails. (IMHO.)
I lived a few blocks from the Western Pacific as a child and used to be at the station two blocks away to greet the passenger trains. I was also a brakeman at the portola RR museum which is dedicated to the WP.
I choose other the Milwaukee Road and Rock Island being my second choice.I am looking to model the Milwaukee Road Iowa Division from Council Bluffs to Savanna and include the Rock Island as if the Rock Island had trackage rights on the Iowa Division.Era 1979--1985.
Most likely will be double track.
I was building up BNSF and than the company was purchased and my stock was gone. so, I purchased NS stock as it was a great deal and now I'm modeling NS. I don't have a layout yet so it's easy to do anything when you build modules for with a group.