Hi,
The older style has the mollex connection similar to there VHO ballast, it's very light, almost zero heat and puts out 20% more light output then a normal halide ballast. It's find tuned for a 10K bulb, so you get near 250 watt output with that ballast. The drawback is it's designed for just the 10K bulb, although they can tune it for others if you send it to Icecap and it was more prone to problems. They keep this ballast because of the high performance marks.
THe new style gives you similar results as a traditional tar type ballast, which just less electric. SO it's main goal is electric savings, not light output. It's big advantages are electric savings and it is able to run any 175watt bulb.
thanks
jason