all this talk about the 600 watt hps/mh,, i did multiple tests on my 4x6 table before i bought cmh.. i was running 2 600 watt hps, then 1 600 hps and 1 600 mh,, the 2 hps had a higher yield but the mix had better quality.. then i did a 1k run,, the 2 600's did way better than the 1,000watt hps.. i then tried 3 400 watt hps and yield was even w/ the 2 600's,, after that i combined 2 400 watt hps and 1 400 watt mh in the middle,, out of all the grows, the combined 400's had the best quality and bud size was more uniform than runs under 2 600's and the 1k.. if i was to go back to hps/mh i would run 400's.. if we are talking a single lamp to another the higher wattage one wins,,however if running multiple lights , like 2 600's or 3 400's both using 1200 total watts in my experience more smaller units get better coverage than less larger lights... i know sombody will now say,,, so 6 200 watt is better than 2 600's or 3 400's,,, my answer to that is I DONT KNOW i havnt tested it,,however logic tells me the penetration of the 200's would be maybe 2 ft,, wile 400's penetrate to 3' and 600's to 3na half or 4 ft, and a 1k 4.5 ft tall plants... if growing verticle this easily means higher wattage = better penetration,, however to SOG or SCROG growers who pack plants in to an area and only grow 2-3ft tall plants multiple lower watt units is the way to go.... i could be wrong..