"The most powerful model is 500watt but only draws 250 and is about 20 times brighter than a HPS 600watt."

Yea, no.

That's taking 2 watt diodes, PWM underdriving them to 1w to obtain a higher efficiency, but still output less than a dedicated full-power 1w module.

PWM = turn around and ignore it, you're about to get gypped for more equipment that does less. Those panels are PURE MARKETING and just to let you know NASA outright rejected any underdriven or even PWM overdriven panel.