on 120v, you'll be using around 10 amps, meaning one light per circuit
on 240v, you're using have the amperage, and therefore can run twice as many lights on the same sized circuit... most 240v circuits are rated for higher amperage as well, so it boils down to how many lights you'll be using. if only one, and you have a circuit for only the light, go with 120v for simplicity and ease.
as for difference, there is none in the operation of the lamp. 1k is 1k