Dealer salespeople are loyal to their brands and shit talk the other brands, so I'd take that with a grain of salt. I own both brands, they are basically the same.

Mitsubishi Electric or Mitsubishi Heavy Industries?

I sourced opinions far and wide and in the end it seemed to be a coin toss between Mitsubishi Electric and Daikin. A lot of it comes done to parts availability, and both seem very strong in Australia.

Mitsubishi is gold standard in cold climates. It’ll pull heat from -30F air.

There's no reason that's unique to Misubishi. My parents Fujitsu has done so.

Both brands trade off as best cold weather heat pumps in ratings/evaluations (quick Google search should confirm), they’re both fairly high quality versus competitor brands.