I believe, from everything I've read, that you need a specific spectrum for the best growth no matter what bulb you decide to use and of course dependent on what stage of growth you're at.

History has suggested that cool whites are the best for vegging, but there are a lot of people these days that are combining different spectrums with awesome results. Most of this though is done while in flowering with them suggesting that the added spectrums normally used for veg helps the secondary growth shoots (and all plant matter) continue to grow and get more robust during flowering.

But if I had to make a choice, I'd probably go with half warms and half cools. Put one warm and one cool in each fixture. That of course being if you have an MH and an HPS bulb to use throughout this process, them giving you the majority of the correct spectrum/light you require. The fluoros just helping out and adding that cool white to the flowering stage. The warm in veg isn't going to make much of a difference as the plant is looking for a different spectrum to grow massive amounts of plant matter.
Marc Benson Reviewed by Marc Benson on . Cool White or Warm Flourescents? I have a closet that is around 5.5 * 2, I have a 400WATT switchable MH/HPS, I also have in there 5 4 foot 2*40Watt Flourescents(Another 400 Watts), I bought these originally, and then decided I want MH for VEG and HPS for Flowering.. I went to the harware store and the cool whites are cheaper, all the sites I read say get cool white, some say mix with warm.. I am just wondering what is best for VEG and what is best for Flowering,,, if you had to choose one, whiich one would it be...?I would Rating: 5