Saw your post in the Kessil AP700 thread about lighting - thought I would post here my thoughts instead of entering into a discussion in that thread.
You asked which lighting people prefer - Kessil AP700, Hydras or Radions. I've owned all three.
First I would ask what type of coral you plan on keeping. I wouldn't use the Kessil for SPS. Currently I have an SPS tank with Radions and a 10 gallon LPS/softie tank with a Kessil A80.
I love the look Kessil's produce (AP700, 360's or A80, they all produce the same light/shimmer), but the thing I did not like about the AP700 (which holds true for all the Kessil lights) is that they come off a bit dull - the tank won't appear bright unless you run the spectrum with more white. Also, the AP700 will not allow you to slowly mix or blend the spectrums as you change colors. Unless there has been a change in the programing of the lights, the AP700 will just "click" over to the next color if you program the lights to change spectrums throughout the day.
Now, if you get Kessil A360's, you can buy the spectral controller and it will properly blend the spectrums as they change colors. It looks a lot better than the AP700, and the actual light and shimmer is the same as AP700. Make sense?
If you like Kessil, and you don't plan on keeping SPS (Monitpora's will probably do fine), I would use A360's with the spectral controller. I think the Kessil out of all three LED lights looks the nicest and gives the best looking natural shimmer.
The Hydra and Radions look very similar - you'll be able to independently control each color channel, but you'll find that you need to run the Reds and Greens lower, whites low and blues high.
The Hyrda aren't as bright as the Radions (unless you run the whites higher). The Radion G4's are bright. I run a pretty blue spectrum and the whole tank is really bright. There is a bit of a "disco ball" affect you hear people talking about, but's I don't think it's bad or really that noticeable. I still really like my Radions.
Hopefully this gives you an idea of what each light has to offer.