I have quotes on these two systems. From what I can tell - the big differences between the two are:

The Affinity (two stage compressor) has a 15+ SEER rating vs Armstrong (single stage) has a 14 SEER rating ( 6.5 tons total - which I have ball parked the savings for the Affinity at $100-$200 a year .. zone 3 - North Carolina ).

The Affinity is claimed to be very quiet ..

The Armstrong can be obtained with a great warranty - 10 year, no lemon - parts/labor fully covered. The quote on the Affinity is 10 year compressor/5 year moving parts/1 year warranty

Am I missing anything in comparing these two in order to decide ?

Thanks ! Dan