[twelve45]

Yeah for the closest possible comparison in your scenario, you want to do a 3 year reserved with heavy utilization.

When you reserve an instance, you are committing to a higher upfront in order to get a lower hourly for the reservation period. The low/medium/high utilization is sort of a knob that allows you to further control this upfront vs. hourly cost. With high utilization you have the highest upfront, but also the lowest hourly cost. If you are planning to run the server 24x7, this will also give you the lowest total cost.