If you're just looking to do a fish only tank the lighting doesnt matter at all. If you think you are going to want to keep corals down the road you may as well get lights now that can accommodate them so that you dont have to just buy another fixture later on. Either T5's with individual reflectors or Metal Halides will let you keep whatever you want. You'll spend more up front this way but you wont be wasting money on a fixture that you're just going to make obsolete later on down the road.