yet another flight school business question

yup... its that time again?! ::)
Which would be best?
Purchase a used aircraft as a trainer which as the benefit of lower initial cost, lower monthly cost etc.
or
Purchase a brand new aircraft similar to a Flight Design CT which would reduce fuel and oil related costs by over 80% - but it would cost more per month.
I have incorporated both options into my excel spreadsheet.
The monthly cost of the new aircraft is almost $200 greater than the used aircraft... however, the fuel use per year of the new aircraft is about 80% lower.
Which would be best?
Purchase a used aircraft as a trainer which as the benefit of lower initial cost, lower monthly cost etc.
or
Purchase a brand new aircraft similar to a Flight Design CT which would reduce fuel and oil related costs by over 80% - but it would cost more per month.
I have incorporated both options into my excel spreadsheet.
The monthly cost of the new aircraft is almost $200 greater than the used aircraft... however, the fuel use per year of the new aircraft is about 80% lower.