Oh yeah, but in all seriousness, no contest, 2x600w.
600w = 96,000 lumens
1000w = 155,000 lumens
2x600w = 192,000 lumens
For 200w you get 37,000 lumens. That's a good deal. Those numbers are sort of irrevelant, but they show how much more light the lights put out. Add in that 600w's ride so much lower than 1000w's and I find I get more bang out of them.
I actually just dimmed my ballast back to 600w and put in a 600w bulb. My tent isn't tall enough for the 1000w.