I think it's great that people do comparisons. Props for conducting some experimentation. Much better than simply speculating what's better or worse. But while better than nothing, this sort of testing and conclusions isn't definitive at all. Obviously full scale comparative testing would require the control of a lot more variables. And testing of a lot more than two bulb brands. I certainly don't totally discount the results presented here, but let's face it, the results could have been influenced by other factors.
At best we could conclude that the Ultra Sun didn't work as well as the Hort bulb. I could tentatively agree with that. Could be a bad lot of Ultra Suns, could be the sum of a lot of things. Those are untold variables. So again, at best this would tell us to avoid the Ultra Sun. That in no way, shape or form directs us to conclude that people should buy Hort bulbs now. I'm surprised that was the message that people came away with. "I'm gonna buy nothing but Hortilux now.." What about Ushio, Phillips, Sunmaster, SolarMax or even a "value" bulb? How do we know that some of these other, potentially significantly cheaper bulbs don't actually kick the Hort's ass? WE DON'T.
After looking at this comparison I'm left with the idea that I would maybe avoid the Ultra Sun, but I am not at all left with the idea that I should buy Hort bulbs. The thread quickly concluded that this was proof that we all should overlook essentially all other bulbs than Hort, which is ridiculous. This informal comparison may tell us that Hort is better than Ultra Sun, but it does not tell us that Hort is better than everything out there.
Having some loose data to compare is great, but we can't logically make such sweeping generalizations.