Truthfully, I've never understood that argument - that held true back in the day, but with today's technology, I don't believe it does.
150,000 lumens/1000 watts = 150 L/W
90,000/600 watts = 150 L/W
Now I realize that a 1000 watt actually uses like 1100 watts, but still, that's negligible to me.
Also, I like the denser nugs and increased light penetration - the only reason not to use 1Ks is because of heat, and it seems like I've got that problem solved (until summertime, at least).
All right, break time's over, back to work