HPS/MH conversion

Up until now I have been using CFL lights and plan on upgrading to an HID light. After looking around, i've noticed that the HID conversions are $50-100 more than just MH or HPS... are they worth the extra coin?
I'm thinking of either getting a 600W HPS or a 400W conversion, anyone have any thoughts on which would be a better purchase?

You could always get a 400w digital ballast and then just use either the hps or a regular mh bulb. They are quieter, use less energy and supposedly the bulbs burn a little brighter as they are more effecient.

You can't really do that with the 600 though because there is only a 600 watt MH conversion bulb available at that wattage. Hope that helps a little

Get a dual ballast instead of a conversion bulb........