direct link to study on the matter if anyone is interested.
I do know i whole heartedly prefer growing plants under HPS or natural sunlight over LED, and will continue to say that the only reason i even use LED's, is convenience of grow room design and setup, and power savings. It is just consistently more difficult to keep a plant in peak health under LED lighting then it is under the sun, or a digital HPS ballast. Assuming temps and grow room design are managed well anyway. Plants definitely dont feed the same, and dont express the same, and deficiencies manifest more quickly and easily under LEDs, thats for sure. I took a bunch of familiar clones with me into LED from HPS and really, i had to completely re-learn them. Some did fine, some were like a new plant to learn.
You have interesting things going on comparing a 50hz HID ballast, to a digital one running at like 20khz too. Even with the same exact bulb being used as well if anyone wants to look into more interesting technical stuffs and how it directly affects the way the plants process elements.
the most effective artificial veg lighting ive used were T5 panels. The most effective artificial flowering lights ive used were digital ballast operated HPS lamps. The highest quality examples of flower ive ever grown though, flowered under mixed spectrum t5 panels. Unfortunately it's pretty annoying to effectively implement any one of these lighting systems to their full potential in a home environment.
We also unintentionally spent 50 years as a culture selecting and breeding our indoor genotypes to perform and thrive under HPS lighting, Not LED, because prohibition + the available technology forced it.
Things will swing in favor of LED over time, but it'll take a while.
