Just wanted to offer my twocents in this debate, as it will never end...
LED's have come along way, from just simple blue's and whites and now full spectrum diodes that seem to produce a good enough spectrum to grow coral.
What I think people forget about sometimes is that having good husbandry skills with your tanks needs is almost more important than having the best lighting systems. I read the post of people like ChrisKid, Pecan2Phat (Warren), Swannyson7 (Scott), KrazyKarl, Franky....every single one of them has different lighting systems
ChrisKid - Full metal Halide with I believe T5 supplement
Warren - All LED's, AI's, Radions, PacSun, DIY's
Scott - (When he had his tank) T5's and I believe basic white/Blue LED pendants
Krazy Karl - Full Radions
Franky - 6 bulb Tek Light
All of these folks, only to name a few have gorgeous tanks, what I feel sets them apart from all the people who sell their LED's...HUSBANDRY SKILLS. All have proven that these 3 main lighting systems work and can grow coral.
With proper maintenance and supplement dosing you can achieve these types of results. I agree that Metal halides are tried and true and produce AMAZING results but LED's also have their dog in the fight and they seem to have a bit of bark to them as well...