I'm looking at some options to replace one of my HVAC units. The one I have is a 5-ton package unit with heat strips (serious $$$ when it runs). It's around 13 years old and is very inefficient. I'm considering replacing it with a 16-seer American Standard Platinum 16 or a 20-SEER Nordyne R6GI (Branded as Frigidaire, Maytag, Broan, Westinghouse). The 20-SEER unit was quoted to me at approximately $1100 more than the 16-SEER unit, but I'm having a hard time deciding between the two largely because there is very little information about real-world experience with the R6GI available online. My contractor prefers the American Standard, presumably because that's just what he's comfortable with; he seemed very unsure of the R6GI unit because he generally doesn't like Nordyne and doesn't have any experience with that particular unit.

Does anyone have any experience with this unit, and if so, how has it been?