I won't go into too much technical stuff about Current and "Chinese box" (and most other) LED fixtures, but I'll tell you why I don't use LED's. The bargain-basement fixtures use cheap, off-the-shelf LED's who's emitters can have a broad spectrum (ie: emitter advertised @ 6000K... actual spectrum @ 6000-9000K), not a specific, steady wavelength. Some of the "middle-to-upper class" fixtures use older generation Cree or Bridgelux chips, but due to either circuitry shortfalls (such as daisy chaining) and/or cheap drivers, they tend to be out of (advertised) spectrum as well. Dimmable LED's... only top end LED fixtures use Pulse Width Modulation to "dim" the LED's, which keeps the emitters in correct spectrum, while all others use current reduction, which further alters the spectrum. Dimming with current reduction also creates extra heat by causing the LED's to use more energy... more energy than at full power. If a fixture has a fan on it, you can be sure that it's using current reduction. If you buy LED for a reef tank and see a chart for PAR, that's all fine and dandy. Is there also a chart for PUR? PUR is far more important to a reef tank than PAR.
Top end LED manufacturers pay premium prices to have exclusive rights to the newest generation LED's, and that's why they are so expensive. All others use older technology coupled with cheap(er) construction processes. They'll often add cool little bells and whistles like cloud, storm, lightning, sunrise and sunset features, and add different colors to make your coral's colors "pop", but these are all sales gimmicks to make their products more attractive. Some people have some success using them for some corals, but the results can vary from one to the other... very dramatically. Top end LED's grow healthy corals by providing the proper wavelengths, so their colors "pop" naturally.
Long story short: I don't use LED's because I can't afford them. I can't pay the premium price quality units demand, and I have too much invested in my tank to gamble that I'll be one of the lucky people who's able to maintain healthy corals with a cheaper lamp. That's why I use T5 HO lamps. Sure, I have to change the bulbs every year, but I can control the spectrum as needed. With my current setup, I have plenty of softies, a couple of LPS, and a couple of SPS. I don't have more LPS or SPS because I wanted to try the current specimens for about a year before investing in a bigger collection. It's been a year. They're all thriving under the current lights. I'm sticking with what works, at least for me. Instead of forking out $1K+ for top end LED, I'd rather add new corals to my tank. Just my 2c...
