Once you get up to the ultra efficiency, there is a large price difference between them and the units below. I have installed two stage heating and two stage cooling. 18 seer AC and 96% AFUE furnace. The energy savings are real especially here in Canada where everything is very expensive. But just as important, the quality of parts are better in the high end models and there is also a MUCH better warranty. Our good friend told us in terms of brand names and their different lines of products, these companies utilize pretty much the same parts, some brands even owned by the same company. He chose to go with the KeepRite because that is what he works a lot with in commercial HVAC and they are easy units to fix.
I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.