I have to say, for all the Mars Hydro bashing, I've just flowered a 4x4 tent on them and I'm impressed.
I normally grow NFT, 5 plants to a 4x4ft tent, 400w MH veg, 600w HPS flower.
Depending on the strain, I get between 11 and 14 ounces. That's proper dry - self use dry - not "nearly dry" to sell. Mostly around 12 ounces. So we are looking at 0.5 to 0.6 gm per watt (my 600 HPS on digital ballast pulls 640w from the wall). I reitterate, dry - I see buds that get sold (someone else I know) and our idea of dry and cured are different, through different motivation.
The latest crop, I vegged with 400W MH, but then switched to LED for all of the flowering phase. I picked up two Mars Reflector "blurple" 144 LED units - the long ones with three panels in each . One is the older 3w led version, and the other the newer 5w led version. I paid around £100 GBP each. Together they pull 540 watts from the wall in full-on mode (veg & bloom both on).
Flowering was markedly different. The buds started with many more white hairs than I'm used to. Very neat. When the buds actually started getting bigger they were much much denser than I'm used to. Very dense structure, more compact and less airy than I'm used to (Purple bud, growing from cuttings used under HPS previously). Almost "knuckle like" in their density. Strikingly different. Also no signs at all of heat stress or bleaching. I kept the lights about 1ft above the canopy.
Because the two rectangular lights fill the space so well in a 4x4 tent I got very even bud sizes across the canopy, rather than the giants being focussed nearer the middle.
I also didn't notice any difference at all betweem the side with 3w leds, and the side with 5w leds. Which wasn't a big surprise as they pull a very similar current from the wall.
I weighed it up tonight. Again, properly twig-snapping dry. Done slowly over 2 weeks. They stink before they've been near the curing jars. 9 Oz. So thats 0.46 gm / watt.
Not bad at all. Not far behind my HPS average (0.51 and 0.60 at best) with a very easy to harvest crop (neat compact dense buds), and all running around 2 degrees C lower than my HPS.
I bought a third light for less than £100 too, so I might try flowering with all three next time.
Are they worth the money at full price? Definitely not. Lower yield for a LOT of money of you bought two at RRP you'd be short of £420, whereas an £80 HPS setup would yield more. But as an experiment, I was impressed. If I lived somewhere where the heat was a problem it would be an attractive option, and based on my simple experiment, I can confirm they are not "shit" / "junk"