Great question!

In terms of electrical efficiency, the heat pump wins by a long shot. They are able to move much more heat energy than they consume in electrical, it's crazy. So heat pumps will use by far less energy. If these machines weren't mining bitcoin, they would be essentially 4,000 watt space heaters.

Heat pumps being able to do heating and cooling is great. Once someone figures out how to use bitcoin mining for air conditioning then thats when things will really pop off haha. I will probably install heat pumps at some point for cooling since I have no AC, but for now the main goal was mining :)