I have not owned an air-cooled generac. Looks to me to be the same "entry level" whole house generator that Kohlier / Generac build. Air cooled, just as loud as a 20KW Generac. It's got an aluminum housing (not all Generac's do).
I bought a "used" 20KW generac from a small data center. It's run flawlessly for about 2 years. It's loud, exercises itself once per week and it's done all we've asked it to do. Longest run time is probably 48 hours.
These home standby units work. They're certainly not as good as the water cooled (commercial) alternatives.
Generac (corporate) support kinda ***** in my experience. Their answer to a "warranty" issue is to take whatever it is (I've had their load shed devices fail) into a dealer and pay a diagnostic fee and they'll warranty it. This is on an item where you can see that the circuit board overheated and controls shut down. I can't ship it back to corporate and have them confirm that it's bad... So I just ate that part and bought a replacement.
I agree with others - lots of this support is going to fall to how good your local dealer is. I suspect there are fewer Cummins dealers.
But if you're DIY - and all Costco, Home Depot, etc all sell direct to consumer - it'd make a difference (to me) if they'd warranty direct versus force to a dealer network.
