Can't really say anything bad about the LG except the price.. I have both the A51-SGS and Cali Lightworks 200w and I prefer the setup of the SGS (seems to have better coverage) and also, it seems more of the plants cross over from the SolarFlare side to try to reach the SGS than vise versa (if that doesn't make sense let me know.)
I actually have a couple 36x20's so I can tell you with certainty one of the few problems you will encounter with the SGS is that the plants will want to grow into it. Another big difference between the SGS and the SolarFlare is that the SolarFlare will bleach anything within 6-8 inches. I also have a 432W HTG that I am not currently using (not quite as strong in flowering I found) but which also filled the space quite well.
That footprint is almost perfect for the SGS, and I doubt you will find 2 people on here that actually own an SGS that have 2 things bad to say about it. I know the fellas at
www.Area51lighting.com were running a hell of a sale, and have really almost gone out of their way to hook me up when they can. Aside from the SolarFlare, I have bought my other 4 lights from A51. I Honestly have nothing but good things to say about them, and couldn't imagine spending my money elsewhere (although I gotta admit, Tags i believe, is doing some serious funking damage with those Apaches.)
Hope I was some help, and best of luck with your LED. I hope some day I can "come out of the closet," but until then I feel these new LEDs have really allowed us closet growers a fighting chance at some "dro." I think the most important thing with LED is buying/making a quality lamp.