LED for sure.
If you want to save a few bucks, either go the DIY route already suggested, or pick up a light from ebay.
http://www.ebay.ca/itm/120-Watt-Aqua...item2c5c86e1a1
Or search for reef lighting on ebay.
If you're not on that much of a budget, go for an Aqua Illuminations... they're about $400 if I remember correctly.