Sometimes it's a question of clearance too. I've found that depending on the types of cars serviced at a location, depends on where I orient my machines. (Real RR's seem to follow this pattern also.) If the cars are very long and swing out over the rails, then it's better to place the machine away from the direction the cars swing (inside of the curve). If they don't swing out, then it's better to place them on the inside of the curve.