I'm saying that both are full spectrum lamps. I have known people who swear by MH exclusively. IOW, it doesn't matter. Choose the most efficient hood you can and go with a 600W HPS for your best bang for the buck. You're buying light. I have been in these age old discussions on light spectrums for years. It comes down to alot of theory and little real world application. You just have to do the experiments. Attached is a spectral graph of an Osram Sylvania HPS.