That's a different kettle of fish entirely, largely because with the heat pump water heater they're pulling the heat from the inside of your house, forcing you to move it twice when it is cold out. With a combined unit you only move it once, as the other side of the unit is outside.
That's why they're so great for warm climates though. The water heater also cools your house, especially as that heat is then lost down the drain. Everybody in the south should be jumping on these.