Answer:
The one that is properly installed by a reliable, qualified contractor. Most systems carry the same warranty; 20years on the heat exchanger and 5 years on all other parts. Sure, there are low end builders grade units, but all mfr`s make them because there is a market so brand is not a factor and you can usually identify the builder grade unit by a lesser warranty. Don`t buy those, unless you are not going to be in the house long. Buy mid grade and up from most any mfr and get a quality install and you`ll be fine. A top of the line installed by a weekend warrior can give you much more misery than a lesser unit installed by a pro. You have to shop both contractor and brand together then go with what feels right. Remember this is for the next 20 years or so and lastly if you go with a lesser contractor he is also your warranty guy.