The topic of LED is very perilous. Efficient LEDs (like Area-51, Tasty, Johnson, GrowGreenLED) can be run at 20-30w/sq ft.
The inexpensive epi-whatever lights you see on Amazon/eBay are often spec'ed at 30-40w/sq ft. But, in flower, they don't work. You have to use 50-60w/sq ft. (I've seen people doing 70 and even 90w/sq ft.). So, at that point, T5HO (for shorter spaces) and CMH (for taller) are better values. For the same money you have a serviceable fixture for life (or something you can sell). And, you run them at 40-45w/sq ft or 35-40w/sq ft, respectively.
If you don't care about efficiency, or how you supply HID-like watts, you can grow with the inexpensive lights. You just have to use more watts than you might have been led to believe you needed. That's a problem if someone expected low-energy, low-heat. (Or, a problem when someone doesn't care, but then feels offended when this calculus is pointed out.).
As long as you know what you're getting into, it's not bad.
Lux could be a reasonable way to look at it, if you're comparing similar light (for example, white light). The problem is that the blurple lights aren't comparable to full-spectrum white, like that.
I like watts/sq ft. 50-60w/sq ft for HID. The power mentioned above for T5HO or CMH, efficient and inefficient LED.
Why are you considering LED? Are you trying to solve a problem like electricity cost or heat? Sometimes people do LED just to be sexy cool. But, they'd be better off with T5HO or CMH. (As long as you know what you're trying to accomplish and can make a cost/benefit decision based upon those priorities, you'll be ok.).
There is an LED forum under the Indoor forum. But, it's heavily DIY. I think the curious don't understand a lot of the discussion there. I think I've summarized what you would be told.