Daiken works efficiently in cold. By the NEEP numbers, they hold 2.5-3.0 COPs @17F where Mitsubishi is generally 2.0-2.5. Doesn't seem like much, but gains in COP mean more at 2 to 3, than 3 to 4, or 4 to 5.
I am not trying to sell air-source, but, conversely, getting hung up on...