Something that readers may not know is that they are now heat pumps on hot water heaters. An added benefit is that the fan on the heat pump will exhaust cold air. That might be a benefit for some folks!
In the north the incoming water is cold which really slows down the hot water creation (recovery) rate, and that cold exhaust then needs to be warmed up by the heat.
If you have low usage (i.e. less than 40 gallon/day of hot water) you could get away with it, but that's two showers - so if your usage is more than 2 showers per day I would avoid them.
But in the south they are a much better choice, since the recovery rate is much better and the cold air helps with A/C.
A big win for me is that I no longer need to run a dehumidifier in those basements. The cold air output from a water heater alone is good enough to keep the humidity down. Again, YMMV.
Unlike an A/C which is split, with the compressor located outside.
They also cease working when the power is off, of course.