.........I'd think it matters how close together they're going to be, how tall, etc.......I mean if your growing trees you need the depth of 1000's or other vertical lighting... if it's SOG style the 600's are great. I believe the rule is a minimum of 35 watts per sq ft up to 50watts sq ft on a canopy/SOG, and some go higher. I always have shot for 45-50wts sq ft and I grow them to about 28-32" and keep the big fan leaves off in flower to help the penetration of light......not suggesting for you to trim off your leaves as a lot of growers dont----myself, I trim everything just before(3-4 days) flowering.....
Good luck!!
gman
