Basically quality of materials and workmanship. Good LED lights are rather expensive up front. I do think that the light movers are a good idea.
IF you get into high quality LED lights, then they talk about the manufacturer of the LED and if really high quality, the bin of the LEDs used. LEDs are most definitely not created equal and even top manufacturers such as Cree and Philips have a great variety in the quality of LEDs manufactured and thus they are binned (separated) so you can buy different qualities of the "same" color. The lesser bins will give out significantly less light and may vary greatly in wavelengths as well. That's just the LEDs themselves...then there's the drivers...heatsink (ha! for the cheap LED lights), (noisy) fans and quality of housing. LEDs which are run too hot will perform poorly for light output, wavelength stability and will burn out quickly.
Things to watch for: Most LED sellers will list the "theoretical" wattage of the LED light even when everything about the unit is incapable of reaching that theoretical level. You want to know actual wattage drawn.
I'm using Kessil H350s with a spinner but I'm building some home made units as well so I can tailor my spectrum for the time of the grow (far blue in veg, deep red in late flower, etc) and for side lighting to possibly fill in some spectrum. I'm looking forward to all the pieces arriving as I've seen some nice results from what people have posted with their diy lights. If you are diy, you might want to look at ledgroupbuy.com stevesleds.com modularled.com
Of course, if you just want to get up and growing...Psuagro gave you some decent recommendations.
