The ATI with 8 T5s on top of the LEDs is certainly a much brighter light than comparable LED fixtures without the additional T5s but when you guys compare the two tanks at concept keep in mind the 8' tank in Dave's office has 2 4' 8 bult ATI fixtures while the 10' tank with GHLs only have 3 units hung quite high, plus it's like a foot wider. It's virtually impossible to get a good comparison there, you're comparing over 1100 watts to less than 500 on a much larger tank.
That 10' tank needs at least 2 more units (more to be comparable to Dave' tank) with all units moved lower and mounted the other way. I think I've mentioned this a few times
That said the ATI is nice but I still think the functionality that comes will LEDs is lost with the addition of T5s.