@ phatjay - For the Karma gear - check out the Karma Genetics sub-forum here on ICm.
But to say how much do they yield...I don't know - how well can you grow? How good are you at the craft?
I personally ran the Brotherhood OG line - Happy Brother x Biker Kush - and I found some great plants. I'm not a mono-cropper...so can't give you relevant number per light to help you quantify your interest in Karma's gear...
But...HONESTLY, If you've never grown anything from KG - then you are quite simply put - missing out on some of the very best cannabis the industry has to offer. There. I said it.
It has nothing to do with hype or being a fanboy or anything else - Karma has a very unique take on what cannabis should be and his plants and seed lines showcase his perspective of what cannabis is and should be at it's very best. Yes, technically the same could be said of all breeders - it just so happens, that I LOVE the TYPE of plants I've grown from Karma Genetics.
I've grown plants from different companies that by all means could have been included in the same pack of seeds they are so generically similar. It's what is becoming "run of the mill" and even though great...still by default becoming average and redundant because it's been done by 20 different breeders.
I'm stating emphatically regardless the genetics involved, what KG brings out of the genetics utilized...will be vastly different from what everyone else produces. His take on what cannabis should be is UNIQUE...and that twist is experienced in all the work he does. Again, if some of his genetics are not in your garden, you are missing out.
Check this thread for a great show:
In the mean time, here's some Brotherhood OG:
1k, 3 gal - organic soil, nothing but water