The lower the voltage, the higher the Amp need, the 220V. unit will pay for itself in the long run trough less curent draw thus, lower electricity bill.
Just take a look at what car companies are developing, 48V. systems, to be able to reduce the size of the wires because they'll have less Amps to handle.
Cause with all the electronics in cars today, dragging around 500 milles of copper wire tends to make thing heavier than need be. My 0,02$.