As Tom states the big advantage to FasTrack is whatever odd size piece is needed for a track plan is available. That is not true for SHS/MTH. Regarding the appearance of the plastic roadbed and variations in the number of “black specs” I offer the picture below. The uncoupler on the right looks different than the converted 5” straight on the left. The iPhone camera exaggerates the difference. The thing is both of these pieces are SHS. There was apparently painting variations between production runs. MTH may mostly look like the uncoupler on the right but I do not have a picture handy of an MTH piece adjacent to an SHS piece.
