The difference in the bulbs is obvious. Most of the higher end bulbs are more of a balanced spectrum, focusing on the blues & reds. Spectrum does matter, try an LED for fun, expensive as shit, but proves a point. You can get it done with a lot less watts/lumens if the light is in the right spectrum. My first grow was with a 400w HPS Hortilux bulb (used 90 days when I got it) & a GE 400w MH. I used both through the entire grow and the plants that were the best were inbetween the two lights. Not directly under the bulbs where the highest lumens were, in the balanced part of the light. Full spectrum lighting rocks! The two most impressive HID bulbs I've seen are the Hortilux Eye Super Blue dual arc. It's a 600w HPS & 400w MH in one bulb. It is incredible. I paid the $225. A big deal for me. The other is the Sunmaster Warm Delux MH. I am almost convinced to ditch HPS for these, great looking light. Not nearly as expensive as the Hortilux. I have used the super HPS bulbs alot, you can tell they are just more balanced than the sickly yellow of a standard bulb. In short, go with either 2 cheap HPS & MH bulbs at the same time or bite the bullet and get a primo bulb. There is a reason it is a multi million dollar industry. Not just smoke and mirrors