Which is the best heat pump brand?

The best installation contractor... You will be happier with a low end or mid range unit installed by a pro than if you and your brother in law or a bad contractor installed a top of the line 98% efficient Trane or Carrier unit. Just trying to illustrate a point here with the you and your brother in law example. Part of the process is shopping for the right contractor to do the work and be around for any warranty or out of warranty service issues. Once you find a contractor you are comfortable with, ask him to quote you one of his best units (all contractors usually rep a certain primary brand). You will find during your shopping that all manufacturers are buying their components from the same vendors: Honeywell and White Rogers for controls, Copeland and Tecumseh compressors, Sporlan and Alco refrigerant control valves etc. So all units except for the low end builders grade are pretty equal and the installation and service which is what the contractor provides will make the difference in your satisfaction over the next 20 or so years.