I think all the testing by the lab people indicate that they work as described, BUT as Star Dog points how - are the results even noticable or do they truly stand out as serious upgrade to "regular" lighting. I don't want to spend couple hundred bucks if I can't really TELL the difference.
I haven't found any research that indicates that UV, for example, has a measurable impact on cannabis but I'd love to read it if available.
The only reasearchers I've found on this are Bruce Bugbee, who touched on UV perhaps two years ago, and, earlier this year, Mitch Westmoreland, a PhD student under Bugbee, who discusses UV in the video he released in which he discusses UV as one of the topics he's doing for this dissertation.
Bugbee's comment was that the research that was done…30(?) years ago by, I think, Liden tested two sets of plants. One showed a change, one set didn't. His conclusion is that the results were "equivocal". Bugbee commented that he did look up the meaning of the word "equivocal" and, based on the meaning of the word and the test results, he wasn't able to say that there was a benefit.
Fast forward to earlier this years and Westmoreland, in his YT video, shares the results of his research and said that they could not find a benefit but, he assured the interviewer, that does not mean that there isn't a benefit it just means that even though they tried a variety of wavelengths, intensities and durations, they were not able to find a benefit.
Overall, Westmoreland recommends that growers give their plants "lotsa light" and present research that echoes what other researchers have demonstrated - crop yield increases as light levels increase so give your plants more light.
He also demonstrates that temperatures above 78° at the flower tops are very detrimental to cannabinoid levels.
I strongly recommend that growers watch his videos. They're a gold mine of "how to" in my opinion.
Back to UV.
I'm buying a new light for the flower portion of my upcoming grow. I'm replacing my Growcraft flower light with either a Vipar SE4500/G4500 or the Mars SP3000. I have no interest in buying UV lights because I've seen zero research that shows that they improve the quality of a cannabis grow. I understand that they're being heavily marketed but, lacking data, my wallet remains closed.
Why would companies sell a product without being able to demonstrate that it has a positive impact on your grow? One reason is because growers want them. They can, also, state that when Liden did his research, UV improved the something something in one of the sets of plants. That's completely true and to a marketing person, that's absolute justification to get products to market.
I don't think companies are wrong to so do - they're offering products that customers are willing to spend money on. And I don't think growers shouldn't spend money on UV lights, after all they're adults and are free to spend their money on whatever they want. And I'm quite sure that growers will say how much better their plants are doing.
The plural of the word "anecdote" is not "data".
My hobby horse is "just turn up the damned light" because there's scads of research that demonstrates that crop yield increases as light levels increase (until to the light saturation point) but that's a different topic.
Re. UV - for me, show me the data and I'm more than happy to write the check. Until that happens, I'll pass.
Only asking to cross reference: added a fairly aggressive amount of "exotic blurple" to a few of our trays and got some very varied results: some cuts had excellent volatile terps some seemed to have gone a bit overboard and the volatiles all smelled a bit like celery. Both the nice and the celery volatiles had the same kind of character in the smell and it would generally go away very fast. The exotic blurple was around 1:1 in uv: 365/385/400 and reds 660/680/730. This types of smells was very new and unique to me; never had it on any other trays, even with fairly deep and high uv supplement. So trying to figure it out now 
