Check YouTube, there's tons of 'bulb tests' that compare different brands, wattages, types (MH, HPS, T5, LED, LEC, etc). It does seem that the 600W single-ended bulbs (MH and/or HPS) seem to be pretty hard to beat in terms of overall performance. Generally, the minuscule difference in performance of different brands of similar bulbs would hardly be noticeable by the end user. I'm using Solis Tek bulbs with a Solis Tek ballast; I believe that it is important to stay brand 'loyal' to ensure utmost compatibility. If I was to change anything I would change to 1000W bulbs; I did use a T5 6500K two-foot four-bulb lamp for germinating, it worked great.