They both make good points. I run a 400watter, and when i first got it i thought 50000+ lumens was the shit! Then i find out a 600 put out around 95000 lumens. But whats the point in havin all that power if u can't keep it cool ya know? It gets to a point where u gotta have the damn light so far away to keep the heat from the plants, that ur losing that effectiveness the further away u go.