My recommedation is to focus on the science. What I mean by that is before consideing what fixture or even type of light fixture you want, make sure you have a firm grasp of what light is necessary and beneficial for Coral growth and coloration. I say this because much of the commentary regarding lighting is not based on the science but rather, personal anecdotal information. For instance, the answers to your question regarding what amount of watts you might want to aim for will be of limited value in my opinion because your coral do not care how much power you are using to generate the light. Watts is an energy input variable but what matters is energy output. So, while there is SOME relationship between watts and output, it ignores the efficiency of the light producing system. Two fixtures that require the same amount of watts... use the same amount of energy to operate, can have very different light output. This is one of the major differentiators between low-end and high-end LEDS.
So, focus on light energy output, not electrical enery input.
Beyond that, not only focus on light energy output but what light spectrum is creating the output. Many use PAR as a basis to measure light output but PAR itself is of limited value because general use PAR meters measure all energy in the visible spectrum and what matters, for coral, is only the spectrum that is useful for coral. So, if the light you are measuring contains a lot of yellow and green spectrum light, you will be measuring light that has no value to coral. This again is a major differentiator between high and low-end LED's as the high-end LED's usually have a more appropriately "colored" emitters. The lower end lights tend to be more "full-spectrum" and include more yellow and green emitters that are wasted light energy from the coral's perspective. This is why you see so many people modifying the cheap led fixtures to switch out the undesirable emitters. If you are comparing two lights that you know have the same or very similar output spectrums, then the PAR value is more useful because you know what frequency of light you are measuring and are comparing apples to apples.
These are just two of the major science-related factors that go into light choices. This science is applicable to all types of light fixtures T5, LED, MH, etc.
people choose their lights for a variety of reasons including cost, appearance, how pleasing to the eye the aurium looks, PAR, spectrum, etc. So it is probably helpful to start by deciding what the criteria are by which you want to evaluate your choices. For me, I try to stay focused on the science and not personal opinion or anectdotal experience or hype.
