In my very limited experience but totally accurate opinion
jk
I would say go t5. I love leds and the shimmer, and color options but from what i've seen and experienced (again limited) is t5 tanks usually have nice colors then led. I think leds have a better actinic color though if that makes any sense. Fwiw and you know this, as fast as the leds are evolving youll shell out for a fixture that will be T12 compared to t5 in a year. I still think leds have a long way to come before I would use them for coral again. I do love them on my freshy tanks though