I use in this order. cfl>MH>hps. But I have use a MH all the way to 4th week of flower, and got one of the biggest yields I ever saw.

I also believe that the light doesn't really decide the sex. I think it is light period, (no more then 16 hrs) and low stress maintenance. Vit B and hormones. "superthrive". i have started seedlings under each type of light I mentioned and have the same high % of fems. Read up on "henks" take on feminization techniques. (Dutch Passion Seeds) The potential of female is in each seed. It is all how you treat the seed. sometimes you lose, and get a male, but "henk" has proven that even with the best "feminized" seeds...you had to create an environment condusive to "creating" female plants. Hope this helps...Peace