Answer:
I believe that it would be better to use the second scale, or 1ft to 500ft.
Explanation:
If you used the first scale(1in to 10ft) then you would have a 75in model, or 6.25ft, this would be to big to display on your desk. If you used the second then your model would be about 1.5in which all though is small it would be better for display.