They both work great. I flower with 4 1000 watt hps lights and have great harvests. HPS is cheaper to buy than good quality LED's by far, but if you can afford the ones that are worth spending your money on, they are tremendous lights. I wouldn't bother wasting my time on anything that would be considered "cheap" in the LED line of lights. Most of the time, you get what you pay for in this hobby. I hope to throw in a couple of 700 watt KIND LEDs in the spring or summer just for the added spectrums. The LEDs do consume less energy and for most, that is the big selling point with them. However, all lights consume energy. You just have to go with what works best for you.
I am going into season 3 using a combination of LED and HPS, I find the LED more beneficial if used during Flower, so I work them in during transition. If you can afford to, you won't be disappointed.
I may be wrong but I've read that with led you get more usable par for the wattage so 600 watt hps and good quality 300watt led would have similar usable light with the led being more focused on par and the hps focused on lumens. Although my experience tells me they don't compare until you factor in heat emmisons. Just imo
the top level Leds and diy cob leds are beginning to surpass Hps in terms of quality flower and resins produced, but the high end double headed hps still reign supreme for commercial weight production and for use by csh croppers.