Most of that comes from what I have gleaned from the LED expert at nano-reef.com. The problem with the high wattage LEDs is that if you look at their lumen/watt output it is actually far less than a good 3 watt Cree XR-E for example (not to mention the new XP-G series).
These numbers are from what I remember off the top of my head so don't take them as hard fact. The typical 30 watt LEDs produce around 300 to 350 lumens vs. well over 100 lumens for a 3 watt cree XR-E. So 3 times the light output but 10 times the power consumption and higher heat production. Very poor efficiency for the 30 watt ones.
Also, they are trying to produce a good spread of light with good PAR and penetration with 4 emitters of 30 watts with no optics which will not give as good a spread and penetration as a larger number of 3 watt LEDs spread out over your tank. Now add some optics to the 3 watt LEDS and you get higher effective PAR and penetration and they will blow away the performance of the smaller number of high wattage LEDs. They are saving money and thus producing a cheaper fixture by using a smaller number of inferior LEDs. If you want MH equivalent lighting then stick to something using Luxeon or Cree emitters with good coverage and optics to increase penetration and have higher PAR at depth. Cree are the market and technology leaders in terms of output and efficiency. The Luxeons are also quite good but a bit behind Cree from my understanding.
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