really comparing a LED and an HPS is totally different. their power is listed in different ways. for instance you can find any HPS rated by watts like 150. an LED system is rated this way purely for power consumption information. and LED system uses the specific light spectrum that plants need to grow, thats why they are made of red, blue coloured leds. So companies compare the amount of these specific light bands given out by the LEDs to those of a HPS. so saying that a 90w ufo will give out more of the plants needed light waves then that of a higher rated HPS system.