you get rid of heat from a 1000w the same way you get rid of heat from a 600! I keep my 1000's 6 inches from the top of my plants! I forgot to move the lights when I went on vacation, they grew into the glass on the hood with out getting burnt! Running air cooled hoods and properly venting your grow, you can keep the 1000's just as close as the 600's. 1000's give denser buds and higher yield. Denser buds weigh more. You get better/denser buds as you move up in lighting.600=buds that are more dense, if light properly utilized, because 600s put off less heat enabling you to put them closer to your buds which means more usable light at the canopy. 1000= higher yield due to more overall light coverage even if kept at a further distance but the buds may or may not be the same quality. using twice as many 600s as 1000s of coarse is gonna produce higher yield and better buts because the light will be better distributed as you have more lights/reflectors and the produce more lumens per watt than 1000s. but ventilation setup/space make this idea more of a problem than it sounds like. ie: a 20' x 20' room with 4 1000s works space-wise and ventilation will be clean and effective. throwing 7 or even 8 600s, just as far as reflector/fan/filter/ventilation space goes, in the same room might be awesome on paper, but when you get that many reflectors in that space...youre gonna realize the problem with trying to sardine pack your lights and othe requipment in that space that 4 1ks wouldve been a much better choice. in my opinion 1000=yield 600=density but thats just from my experience.
You don't wear sunglasses in your grow room?as for lighting its so fckin bright that once you walk out of the room your blind
That's about the best answer yet. I'm just prejudiced, 'cuz I just LOVES my 1K's, but there are some applications where 600s are the best answer. MY answer would be to enlarge my space rather than reduce the light, but I realize that not everyone has that luxury!!The first step to deciding this is realizing that there is no "better overall" option here. There is only a better option to the situation you have as far as actual growing space is concerned. It is true that a 600w bulb does product more lumens per watt than any other HID wattage. This efficiency does in fact allow you to run 2 lights vs 1 1kw light for just around 200 watts more and maybe a tad less depending on the ballasts being used.
With that said, now the factor of space and even coverage does come into play. I have a 6x6' area lined with orca film and a 1kw hortilux hps in the middle with a reflector that provides a good pattern for moderate spread and penetration over the area. I did at first try 2 600w for the reason your mates had suggested but I ran into a problem. With my area size, I had a region in the middle where each of the lights spread intersected. The result was uneven growth; being wild in some and lacking in others. The 600w had spread the light very well but would not penetrate like the 1kw. After replacing with the 1kw, I got the right combination for my area by having a very even spread with better penetrating power.
Some insight from someone who went through something similar I think JUST FROM MY EXPERIENCE 600w would be well suited to equal 3x3 spaces in a rectangular formation or 4 in a 6x6 which has 4 3x3 areas. Just some insight.
-PE