a medical grower I know uses 1000w metal halide with 600w hps in flower in one large cooled hood. the metal halide ALSO puts out UV radiation, which the plants LOVE in flower. It's what really develops the trichs.

red develops tight buds
UVB develops trichomes

I single plant scrog and flower 3 at a time under 6 4' red T5s plus 2 26w CFL 10% UVB reptile bulbs and a 30" 10% t-10 tube. All in a 5'5 x 26" closet. I know I don't have enough red, my buds are looser than I'd like, but my trichome production is really good.