So with the general advice being 50-100 watts per plant and 50 watts per square foot that would make a 600w scrog grow on a 3x4 foot screen with six plants the exact upper side of those recommendations. My question is whether that limit is suggested as a reasonable practical limit or if using a 1000 watt light with the same setup would be worthwhile.
So I'm going to assume there wouldn't be a big enough difference to justify the extra expense and cooling issues.
No one's said anything, so I'll let you know my thoughts. I'm only on my first grow and went with a 1000W dimmable. Personally I'd say go for it with the 1000W. I love mine, and the plants do too. Obviously I can't compare, but I've got some very nice sized buds going from just bagseed. http://forum.grasscity.com/absolute-beginners/1133802-first-grow-3.html I like the 1000W. Just get one that's dimmable, and then you can turn it down to 50% or 500W if you want. Of 75% (750W). I like having the extra power, and it certainly seems like the plants like all the light. There's heat issues with a 1000W, but if you can keep that under control, then it's worth it IMO. Just remember if you get a 1000W it doesn't need to be close to the plants. You should keep it at least a foot away. If you have the height and can keep the heat down then I'd definitely go with the 1000W. It's not so much that your top buds will be bigger necessarily, but more light will get to the bottom buds for sure and those will be bigger. Personally I wouldn't want anything else.