depends what you are looking for. some people will say (and i agree) that if you flower with a MH you will get a higher grade buds, it will definatly make them more frosty because of the UV light MH's produce.
HOWEVER wat you gain in quality you will definatly lose in yeild. your buds will not be as compact and therefore as heavy.
so if your growing for profit, hps all the way
if your growing for quality MH isnt a bad choice, or even a dual spectrum bulb.