Somebody on here mentioned the other day that people tend to shop for watts, which is a bad mistake. I agree. Wattage is a measure of work. Wattage is NOT A MEASURE OF ILLUMINATION. Motors are usually rated in horsepower, but they can also be rated in watts. What, you say? That's right, google horsepower to watts conversion. One HP = 746 watts.
A device's rating in watts only tells you how hard the device is going to spin your meter. That's it. If people want to believe that the CannonFodder 2000 is better than the HappyHappy Tiger 1900 because it uses more watts, then that's how the sellers will pitch them.
I'd like to point out one thing in the marketing for that dhgate "2014 best Mar II" light. Well, two things. Right at the top - 900W. Holy cow, that's gotta be one serious light. Where's my credit card. Oh, no, wait, it's really 445W +/- at 110V.
Scroll down a little. They claim a lumen output. Lumens are a measure of light as perceived by humans, not plants, but it's more useful than wattage. 24,300 lumens. 24,300 lumens divided by 445 W = 55 lumens/watt. That's pretty darn uninspiring. 55 lumens/watt is CFL territory. Any off-the-shelf Home Depot LED does better than that.
Of course, who knows if the light actually puts out 24,300 lumens. I'm giving them the benefit of the doubt.