When I placed my preorder for the GGD Powhatan Arrow seven car set, I sold off all but three of my MTH 18" N&W Passenger cars. One set each heavyweight, and streamlined. It all came down to "what do you really want". For me, I would prefer to have fewer, but correct cars for my consist.
It wasn't either a money or "newer is better". I also have a lot of 70 Ton MTH Premier N&W hoppers. They're as good as gone if affordable N&W proper coal hoppers become available. My focus has changed to prototypical, scale.