I've been growing LED for three years now, and will say, one light covers about a 4x2 area which is why I run four in my 4x8 and that's not accounting for any cross lighting which is definitely happening. Can't speak for cob, just never tried it, heard it was dope. If I could give you any suggestion, in which I noticed full body results from, is switching my veg cycle from led to power veg t5. I only run 4 bulbs from a 8 lamp fixture and even that has done wonders. Since you're just starting out, deal with your setup for a bit longer, have your friends get into your product, and then go purchase yourself something worth waiting for. I can't even express the inter node development from a t5 and only running 4 bulbs will not give you a big burden on your utility bill. And yeah one might think, you're only running 4 "300" watt lamps....I know I'm not getting yeilds like you hps guys, but the key is to train your plants,l with LEDs because they DO lack lumens and output that a HpS or MH can give you....
Mars hydro 300w, and 600w are perfect and idea for my setup and the quality and yeild don't lack because I put the work into my veg cycle.
@Irietime he runs leds, and I've seen amazing quality come off his grows, check out his bare bones thread in diaries he's got a nice new set up in the works