its even better to use both as you will cover a wider spectrum of light! you can even buy lights with a bulb of each in. As said above MH better for VEG as it covers the blue side of the spectrum which stimulates healthy leaf growth and HPS for flower as it covers more or the red and yellow spectrum which promotes better buds!
Tomthehippie Reviewed by Tomthehippie on . Lighting Question is it alright to use HPS along with MH during flowering? Rating: 5