I'm just curious as to what everyone else uses? it seems most ballast's are compatible with both 120 or 240, but does everyone use 120 because its more convenient or do some guys/gals wire in a 240v outlet. And is their any specific reasoning to using the 240v setup over the 120v? I guess my old light was only a 120v so I never had this option before.
What's the "normal" household voltage where you live? Stick with that. Whether you end up with a 120v or 240v system, the wattage you draw will be the same. The main advantage to a 240v system is that it can draw a lot more power from a single circuit because it is only half the amps (amperage x voltage = wattage). That's helpful for a single big energy user like an electric clothes dryer or electric hot water tank. But if it isn't the "native" voltage then it could be expensive to wire up for 240v in a place that typically 120v (like the USA). 240v might prolong the life of equipment like ballasts, but you'll spend more on special wiring than you would on replacing a ballast that (hopefully) will last you for years.