I would'nt be able to compare the two. For my money I just picked up 1000 watt switchable HPS or MH with two bulbs and two refectors for $219.00 delievered with free shipping. Its a nice unit with seperated ballast/ capacitor. Been working great for 6 weeks. I got 2 HPS but if you call them I'm sure you could get one of each. Same price for 600 watt.
Check it out: http://www.atlantishydroponics.com/Complete-MH-and-HPS-Lighting-Systems/Complete-MH-and-HPS-Lighting-Systems.asp