My two cents.
You are trying to emulate the sun. Now it is hard to compare a light bulb to the sun, but Halides do it much better.
First, the fact of the matter is, halides are point source lighting. The filament produces the light inside the charged glass container. Light is coming from the mainly light filament which is a very small source. Flourescents spread light across the entire tube by the gas that is filled in the tube, spread out greatly. The sun is a point source light. Placement of halides over corals is not as an important concern as some may lead you to beleive. The fact is, the angle of the sun as the Earth rotates constantly changes, so corals are always experiencing different point sources of lighting and reflection, just like in your tank, sort of anyway.
Furthermore, the ripple effect, just like the sun creates in the ocean, is emulated much more accurately with halides than flourescents due to this point source lighting and intensity.
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