Even in a few years 600w of LED will draw as much power as 600w of HID... What is heavier, a ton of lead or a ton of feathers?
You'd think so, but this isn't exactly true.
A nominally rated 600W HPS lamp actually draws around 640W, give or take a bit, because the ballast also uses its own energy in addition to the bulb.
Meanwhile, LED lights are typically rated by the total MAX capacity of each LED diode. But in fact, they're typically NOT run that hot, because the diodes get too hot and this shortens their working life.
So in fact, an LED panel labelled as 600W that is built from 200 3W diodes might truly only be drawing 400 watts. There is no real standardization in how the manufacturers label their products that way, but right now MOST of the LED panel makers do NOT label their products with the true power draw.
In sum, a so-called 600W LED probably isn't drawing the same current as a 600W HPS lamp, even though they have the same "number" attached.
As to which is better, I've looked into this quite a bit, and in my opinion, HID lighting still offers the best spectrum and value/performance ratio. Which isn't to say that LED lighting isn't OK, and still improving, but except under certain pretty specific circumstances, I think HID is *generally* better.