I have sold many different brands of Equipment over the years and have found all of them have their weak points. When I took over the business from my father, we sold Carrier, Trane, Lennox. Now, we still sell Carrier and some lennox, but I have since dropped Trane and am using much more Amana. I have even talked with the folks at York UPG ( York, Coleman, Luxaire, Guardian, Evcon brands) since they have a factory right here in town and distribution center. To me, it is important that my Brand/Distributor takes care of me so I can take care of my customer. That means letting me know when an issue arises with a product so I can get it corrected for my customer. That means providing me with parts/upgrades/new unit if need be and not having to go back and ask more from my customer. As Mdshunk stated, components inside are made by a couple manufactures like Honeywell or White-Rodgers with what ever variation made for specific manufactures. Many brands use a White-Rodgers ignition control although still a few proprietary ones out there. Copeland Scroll compressors or Bristol compressors are used except for Trane/American Standard recips which are their own. You won't find anything other than a GE ECM motor in any brand of residential variable speed furnaces. What makes them "different" is how the manufacture has the power head programmed for their brand of furnace. That's why I say "shop for a contractor" to find one that is looking to take care of you, not just feed you "Brand X is the best and Brand Y is a piece of junk" pitch.