Hey Man, thanks for taking time for this post. Very interesting.You hit it! When comparing or evaluating a lighting system it is far more important to look at the wavelength of the light it produces first and foremost. If you look to the quality of that spectrum is too ensure that the light it produces is of quality for the corals health. Secondary is to look at amount of photons produced and this can be in PAR, most common in the hobby, or lumens, less useful.
So let's look that the most popular and/or most know bulbs for producing healthy corals.
MH Radium, produces a very broad spectrum however most is in the 380nm-460nm.
ATI Blue Plus, another bulb that had a general broad spectrum however most light is also in the sweet spot of 400nm-460nm.
Now, let's look to the Kessil AP700 as a known and quality light. It also is capable of a broad spectrum with majority of light produced in the 380-460nm wavelength. You can also see that no matter then spectrum you choose, with Kessil Logic, it will still produce the majority of correct light for coral health. Also at the bluest settings the spectrum is really hitting that 380-460nm well.
So as you can see what all these have in common is that key spectrum 380-460nm range of light for coral health.
Now let's compare PAR, that's the easy bit. With any number of T5 bulbs you can produce as much PAR as needed/wanted.
The Radium MH is well know to produce high PAR number with either the 250 or 400 watt light as long as you choose the wattage needed for the depth and size of the tank.
I am here to say that the Kessil AP700 has no problem producing PAR numbers of 4-500 in the middle level of 12" depth and minimum of ~150-300 PAR for a 36"x24" area and 24" depth depending on mounting height and even more of you use more fixtures. For me I also use two T5 Blue Plus and I don't have a place in my tank I do not get 300+ PAR.
So each light can produce the amount of photos we generally see are required for SPS and even acros.
I see no real value in even determining the "Best". They all are equally capable and the bottom line is personnel choice.