Tough question man, Mh is always gonna be best for veg and hps is the same for flowering. If you want to go with 1 bulb get a duel spectrum or better yet get a ballast that is Mh/HPS switchable. If you are gonna pick between hps or mh the entire grow then go with the hps.
They make a duel spec bulb but you have to have a 1000 watt ballist it's 600 hps and 400 mh they are perfect for both that's why they made it plant max makes one for like 90 bucks Sent from my iPhone using GC Forum