In our experience, Kongs (the importer of aquaone here in Australia) have been unbelievably good with their customer service and standing by their product. They've replaced two entire AR400s for us (yes, the whole system!) and we chose to go back a third time because of their superior service.
We're upgrading our lighting to LEDs though. Reason being: we wanted good lighting for corals, but also cost efficient lights. The quad unit that's currently on the 400 has a total of 216w. If we added another 2x lights to that, that's 324w plus we'd probably have to do some decent mods on the hood to accomodate them. Add to that our need to consider our best option for no less than three tanks (after just receiving an exorbitant power bill) and our decision was made.
The 4' LED that we're getting (illumagic blaze) is approx 200w for more intense luminosity than 6x T5s and it's completely programmable, we can't shatter a light tube by bumping it during re-scapes, the mods on the hood should be minimal and we'll save power.
At the end of the day, I think it's more a question of what suits you and your tank/lifestyle/budget more than "which light is better" b/c like you said, some people are opting to return to T5s where as others swear by LED's. It's all personal preference :)
Good luck! And your tank looks great ;)