Either will work....MH will keep the nodes closer than HPS for vegg stage. Most usually do switch to HPS for flowering, but you will get near the same results with MH all the way from seedling to harvest. HPS light during flowering usually keeps the bud structure more compact than MH from the little bit of experience I have with MH lighting. Plus the same wattage HPS bulb is gonna be more lumens than the same wattage MH.
I myself just use a enhanced spectrum HPS bulb after sprouting the seeds under fluorescent for a couple weeks. It gives you 30% more blue spectrum than a normal HPS bulb, so it's the best of both worlds in one bulb really.