I have seen scenarios with a huge diference in quality. Some scenarios do not add anything in gamepaly you cannot do with an ordinary timetable drive. In this case, why waste money to write a scenario? Scenarios do not use layers or swap engines if you buy additional content. So my suggestion is to include scenarios only in case: They offer additional gameplay you cannot add in the timetable like cold boot, refuelling, using multiple engines in one scenario Or they have a tutorial nature. In any other case I prefer to have just one or more additional timetable drives.