I must acknowledge the fact that some manufacturers are harder to get parts and "cooperation" from than others..........so, if you buy "brand x" and you live in a small community with "Orville Heating and Cooling", and his "brand x" can only allow him or another authorized dealer doing the maintenance. and the other authorized dealer lives four counties away and has no interest in coming to help you..........you may have problems. I underline "may" have problems. If Orville is a highly reputable contractor, and these guys are out there, he will take care of you. But, sometimes, when there is no compitition, Orville gets lazy, or has to hire "today's" help............need I say more..............and things go to pot. If you use a brand that allows other suppliers to work on your equipment, then you have some options. Options are good. I can't tell you the number of times that I have heard individuals wish they had researched this issue.
Ask the questions..........can "anyone" work on this equipment......or does he have to be licenced by the manufacturer? If they say "no, we have to work on it".........think twice. Better yet, get the 1-800-000 for the manufacturer and relay your concerns to them. Remember, some manufacturers have fewer restrictions on repair, replacement, and warrenties than others. With today's technology, many of the products are quite equal in performance. Again, research, like you are doing, is the right direction, and the only problems you usually run into are due to the "bad guys", which may not exist in your neighborhood, but they "are" out there.