I'm kinda lost on where this is going and how it got here, but one last point for the at600...if 1/4 of the goes out...you still have 3 in there working. All their own drivers. Actually 8. 1 driver for 3 cell clusters. So I would still have a good amount of the light working till I get it fixed. And AT would cover any issues. The only thing that is different than a quick fix version is that you need to solder instead of quick connects. Nothing anyone one here would have an issue doing. Some people, like a few of you here, like to have multiple units. And I totally understand. I will have multiple lights next run so I will show everyone if there is a difference.
Honestly the talk of what if it fails is good, but I can tell you my 10 at120's, an at200 and a at600...nothing has ever been wrong with them, and the at120 ran for years straight. My professor runs his 24/7 and 18/6 for since 2011, he is a clone guy. Yet he did the best flowering run I know of with them. Skills period and good light.
I have said it many times before, just use the search function, when getting a 1 or a couple lights, a51 is the best value for the price. After that the at600 becomes an option and is negligible in price difference. Then when price isn't an issue so much per say, the design is truly on what the person believes or trust will do the job. It's up to everyone to make their own decisions. The more grows that happen and get documented the better.