It really depends on what type of coral you want to keep.
I run T5HO, but my tank is mostly LPS dominated. And I am required to replace my bulbs yearly.
There are Power Compact fluorescents, which are similar to T5, but create a little more heat and a little less light.
An older tried and true light is Metal Halide for mostly SPS dominated tanks, but they create a lot of heat, and bulbs are expensive and also require replacement yearly.
The new breed of light is LED. Less heat, no replacement ( virtually, 10 year life), but almost too powerful for LPS, unless you acclimate very carefully. And can be quite pricey, for the better ones. There are cheaper options for LED, which I've seen good results from in pictures, but for the most part, the jury's still out on LED.
If given the choice, and money wasn't a concern, I would go with Ecotech Radion LED's, or Al sol LED's. This would allow me to grow ANY coral I wanted, but for my set-up, this would run me about 1500-1800 bucks!
Hope this helps.
