i am by far not a lighting expert, all i can say is i get better nugs from mh than sodium.
Your experience is unique. Wonder why everyone else gets better flowering growth with HPS, don't you?
I'll suggest that there is some other difference between your crops flowered with MH as opposed to HPS, aside from the light. Unless you did the comparison side-by-side, you can't assure that all other conds in your comparison were equal.
In flowering, we're looking to mimic light of a spectrum seen in late autumn in temperate latitudes, to which cannabis is indigenous. High solar angles in late spring & summer, while days are long and the plants are vegging, permit more transmission of blue light. As the season moves on to autumn from summer, the angle of the sun in the sky lowers, meaning that the sunlight is passing through a longer path through the atmosphere. Water vapor and particulates in the atmosphere tend to scatter short-wavelength blue light. The longer the light's path through the atmosphere, the less blue makes it through to the surface. You can see this effect any day of the year at sunrise and sunset.
This is why cannabis plants flower better under the red-yellow spectrum of HPS- it mimics the spectrum of late summer & autumn sunlight. It's also why MH, with its comparatively high amounts of blue, works better for veg.
Runs 300mm off the tops. There were 22 more buds like this one in the same batch. 
