With a little bit of creative control work you could utilize all five speeds for various purposes. You could have continuous air circulation (and continuous filtration) on the lowest speed, you could use the highest, or next to highest speed for "normal" A/C with the next step down used for additional humidity control. All this is assuming that the ductwork is properly designed and installed and also that the A/C unit itself is properly sized.
A downside is that the variable speed motors are definitely more energy efficient than the multi-speed motors. Whether or not that would play a part over the life of the air handler would depend on how, and how much, the unit was was used. In my area $750 will buy a lot of electricity.