The honest to god truth is, they all work except for the really underpowered ones using 0.5 watt leds. The MarsAqua at $100 makes light just as capable of growing coral as a $800 EcoTech Radion. Over the last 6 years I've had some experience with most of them.
What it boils down to is what options you want to pay for. These options don't really make the light they produce any better at growing coral, but they give you more control if you want it.
Basic is 2 channels with manual dimmers, at $100 to $250 and there is absolutely nothing wrong with them, A $100 MarsAqua will grow coral just fine. Then a step up and you get 2 channel fixtures with built-in timers and digital dimmers. The next level gets you a controller so you can do sunrise/sunset/moonlights. This does nothing for the coral, but it's an option many people (me included) like. Finally there are the multiple channel controllers so every color led (6 or 8 typically) can be controlled and ramped up and down individually. So you can really tailor the overall color of the light in the tank. Does this make coral grow faster? In a word, NO. But some of us (me included) think we know so much that we can mix the colors better than the basic 2 channel fixture manufacturers, so we pay through the nose for the chance to try. Or, some of us are so picky about the ascetics or look of the color of the light in the tank that we pay for the ability to make it just exactly what we want (this isn't me)!
In short, your corals really don't care that much, they all work. It's really all about the options you want to play with and the overall look, and to a lesser extent, the quality of the fixture. And 99.9% of the people here will tell you the one they own is the very best. There is no overall best, just the one you like the best for your budget. Those are not the same thing!