I am new, but read alot and asked before i bought my bulds,
both bulbs can be used for the whole grow, M.H. would be a faster grow from what im told but for optimal grow it would be M.H. for veg, and HPS for flower, HPS would be a longer grow because the veg stage would not be as optimal, but it would work....so i bought both bulbs and it is in flower now. but the MH just jamed in veg state, and now HPS seems to have slowed the grow stage!