[ZPaul]

The variable speed units will have a lower operating cost. Cycle on and off less resulting in more consistent temperature. Dislike getting a discontinued refrigerant, but expect it to continue to be available for reasonable life of units, or a substitute will be made.
Are the variable speed units not available with the new refrigerant or is it that the "contractor grade" units are not yet available? Contractor grade units are sold to developers at a lower cost than the retail product but generally have inferior construction. Since most developers put in the cheapest stuff regardless of efficiency, producing contractor grade equivalents of more expensive units may not be a priority for Carrier.