oic,
well hps has a better spectrum for flowering, so i would guess it would be a bit better, but the mix hps/mh is probably nice for the guys in the middle.
as far as 600 vs 400, i think you will still see a fairly big difference in yeild, but i have never used a volks with a 400 so i don't really know.
600 is nice but i suspect it can handle more. a bunch more.
well hps has a better spectrum for flowering, so i would guess it would be a bit better, but the mix hps/mh is probably nice for the guys in the middle.
as far as 600 vs 400, i think you will still see a fairly big difference in yeild, but i have never used a volks with a 400 so i don't really know.
600 is nice but i suspect it can handle more. a bunch more.