LED can grow coral. You will see that all over the place. It is true. The story does not end here. There is a ceiling with them and acropora, but not so much Montis, Birdsnets, Poci and Stylos (MBP&S) and some stags... the best setups can get to within about 75-80% of what they could with Metal Halide, but they could provide other things that you like more like thunderstorms, couch control, dimming, etc. Black boxes can do fine-to-good with acropora. I do not think that they do any better that. You hardly ever see people go beyond "LED can grow coral" and talk with any kind of nuance about how the are better than this - to the contrary, anybody who was at Dr. Joshi's MACNA talk will remember that he basically said that his Radions were not as good as his old MH, but he was keeping them since he liked other things about them.
This whole question comes down to two things, IMO. First, are you experienced enough to tell the difference in 80% tank and a 100%? If not, then don't sweat any light choice. Second, do you care? Most people cannot even tell the difference and there are some that absolutely can... and some of those that can tell do not really care.
I might use a panel-type LED for a softie, nem or LPS tank, but for my acropora there is no way... but I walk into WWC or Vivid when I am on the coasts and think to myself "these tanks are 80% of what they could be under better lights..." I can tell the difference.
FWIW - I got a MH for the contest for $62.50 (two for $125 and I only need one). Cannot even get a black box for that, but they are not much more for a decent one. 60 cube, 2x2x2 and perfect for a single 250w MH.