MH VS HPS

I've been reading about grow lights over the past couple of days. I know I have seen you can or should be using flourescents in vegetation. But I also read a while back about using a metal hallide for vegetation and HPS for Flowering. My question is I tried this and it seems with a MH I don't get as much growth. The plants end up being small, I actually ended up putting back in my HPS. It would seem to me that the bigger the plant the more yield. Is this not the case? Has anyone else noticed not as much growth. In the past I have always just used a HPS all the way through, and then tried the MH with vegitation and was kinda dissapointed. Anyone?

I start with some 65 watt Fluoros and then do HPS all the way through

but the reasoning is that MH's have a better light band for the plants

The HPS is heavier in the red light area so plants 'stretch' (i didn't have this problem)

note: HPS bulbs last twice as long vs MH bulbs