I personally believe, (can't prove or even show data), that most of the bulbs are almost exactly the same. Reason being, is there are only so many manufacturers, using the same technique to make these bulbs. I think the "grow bulbs" are drastically over priced, to make it seem like you are getting something that you are not. I mean even if the difference is 10k lumens, thats still not worth the $60 or so extra. I have purchased all the bulbs that I use from electrical supply stores, with the exception of one that came with the HTG $120 400w system. The 400w bulb I have from the electrical supply store seems just as bright, and on the same spectrum. BTW I paid less than $20 for the 400w's and i think about $60 for the 1000w but I could be wrong on that one as it was about 4 years ago that I purchased it. (only been in operation for a few months tho)