Which one out of the bunch, today, boasts the highest efficiency?
I'm under the impression that it's the LEC but would like to read your thoughts.
LED!
On paper, you'd be better off asking the LED guys, as long as they downplay both side equally the comparison should still make sense.
When you ask me about efficiency I'm not talking wall-plug efficiency or luminous efficiency but how efficient a bulb is in growing both quantity and quality MJ in a given space. And with quality I'm not just talking frosty dank but compact and large enough it can be trimmed to commercial quality bud. Specifically, something I know a coffeeshop would buy for more than the lowest price, and hence something I'd buy at a coffeeshop.
The HPS has a bad spectrum claim is in practice not true. It's based on a limited understanding (not here specifically but in general) of photoreceptors. The focus on blue and red is partly because their role is more clear. That doesn't make the rest useless, not even green, especially at high intensity light. I haven't even included that in my comparison earlier... imagine what I'd be growing if that useless yellow of my old hps bulb would be blue and/or red instead... according to led bible number, not me...
The CMH bulb is developed for the US market. It's available here, but still rare. Being that phillips and gavita in NL no longer supply to dutch growers I think it may become a popular import product. For smaller growers. To replace a 400watter or for veg light.
Gavita/philips is good for 1gpw+ of compact commercial quality nuggets. CMH supposedly results in frostier bud. So do PK boosters, supposedly. It's known red directly affects fruit size in many species, perhaps you just get less bud but the same amount of trichs... on leaves... lots and lots of leaves. Besides that, I have no problem produce white bud under HPS...
Simply put, I don't know man, I don't have enough data (as in real world result not bibled numbers) to compare yet. I'm leaning towards 2x 315w myself so I can build a rectangular closet instead of square. Either that or a gavita 6/750 (which I may have to import as well...) or another year of Phillips GreenPower SE 600w, which I can pick up at a local shop. The market is messed up here at the moment and I'm not in a gpw or efficiency race so I might just wait for that Gavillips hybrid light lol
Oh and I agree with churchhaze, LEC and LED combined is one of the best routes at the moment. CMH can be used to supplement HPS as is done (and by phillips recommended for certain species) in large scale grows with HPI-T MH, but with a small amount of bulbs you can never get a uniform spread of the spectrum. A HID in the middle with LEDs around it however... that allows for some interesting possibilities.