Volts and Amps

As long as you can draw enough current (amps) from the battery, you can get the same amount of power out of many voltages. So theoretically, the higher voltage doesn't mean more power in and of itself. Voltage numbers like 40V, 80V, and 120V often represent peak (max) volts.

Is higher or lower voltage better?

A higher voltage means a lower current for the same amount of power. A lower current means smaller components and thinner wires, thus making it cheaper and more efficient. For example, take a DC motor. For a 12V motor to develop the same amount of power as a 24V motor it would have to draw twice as much current.

How does voltage affect power?

If there is an increase in voltage, the power will quadruple. If you increase the voltage (or electrical pressure) in a circuit, then the current (flow of electrons) will increase in direct proportion, eg if you double the voltage the current flow will double.