Dick,
For me it's a combination of both. If the track looks good, and works well, then I'll use it. Over the years, my "standards" have gone up. What looked good to me in the past, has been replaced with newer and better stuff. With TS12 now, I am replacing all my track with Jointed Rail - built-in track, which looks really nice and has great performance as well especially with the new stitched spline method used for creating them.
As time went on, particularly with TS2009 and up, the older track used to disappear and cause objects to disappear because the track splines were too resource intensive. After upgrading the track, areas where buildings and trees disappeared, or popped in and out, are now rock solid.
John