I like to use a mixture of cool whites and soft whites. I found this helps my female ratio. but that is just my theory no fact behind it. Soft whites tend to run a little hotter than the cool whites.
Soft white give out a little bit of the red spectrum and the cool whites give out more of the blue. I like to give a full spectrum of light during veg. but again thats just me.
thx Mutt maybe Ill buy some. I'm doing a stealth grow and I need something small but good and not too expensive. I have some copact flouros right now but no ballasts... and I have 2 working 15 watt reg flouros with one speacial 40 watt grow flouro