basically HQI Metal Halide lights have a stronger output and deeper water penetration than standard output fluorescents. While they generate much more head they offer a more true spectrum and are more comparable to the sun's light than a NO
That said wattage and spectrum are the key in keeping any reef tank, and metal halide lighting is not without its major disadvantages. First Halides produce a lot of heat, use a lot of electricity, and are very expensive for both fixtures and bulbs. In addition to that thier life span is not nearly as long as standard flo bulbs.
If you are planning a reef tank without using metal halides that is fine, I personally have shied away from using them - though I would not recommend standard flo fixtures and bulbs. You would be better off using VHO
flo light, T5 Flo Lights, or Power Compact Flo lights. In addition that that you would never want all your bulbs to be 10,000k daylight, you would want an equal mix of Daylight and Actinic Blue Lighting.
As far as Current USA's orbit fixutes. I personally use the Oribt 36 inch with 384 watts of output and think it to be one of the best fixtures on the market.