Hi David
The 2nd and 4th locos use 'basic' textures without any shading (shadows, or normals maps), or actual weathering (the 2nd loco uses a 'dusty' looking texture). The 1st and 3rd locos (both the same loco model, my VR T class) use baked shadows and normals maps, with weathering.
The actual colour of the models is different as well. The 2nd is a 'faded' VR blue, whilst the 4th loco has the old Auran 'S class' colours which were too bright for the VR blue and gold livery.
Zec
The 2nd and 4th locos use 'basic' textures without any shading (shadows, or normals maps), or actual weathering (the 2nd loco uses a 'dusty' looking texture). The 1st and 3rd locos (both the same loco model, my VR T class) use baked shadows and normals maps, with weathering.
The actual colour of the models is different as well. The 2nd is a 'faded' VR blue, whilst the 4th loco has the old Auran 'S class' colours which were too bright for the VR blue and gold livery.
Zec