With what lighting? If you are at 78-80 with fluorescent, you will be significantly higher in the summer with MH. LED is much more energy efficient, both in terms of watts/coral growth per dollar and in terms of not having to run a chiller or run your AC all day. MH is a proven entity. LEDs are still evolving (they seem to work pretty well, so far, but new twists are being introduced all the time and you may still need to upgrade (or at least feel the need to) in the future. LEDs probably will never need to be replaced in the lifetime of a tank, MH bulbs do, and they're pretty expensive.