T5 vs Halide help

I need some input on choosing between two light fixtures for a 75 gal reef tank. I'm looking at either a (6 x T5 324w) fixture or a (4 x T5 plus 2 x 250w metal halide 716w total) fixture. I'd like to have the ability to keep whatever I want (lps, sps, clams, etc.) I see pro's/con's to both. I like that the T5 only fixture will be cheaper to run, but I'm unsure of whether it will do what I want. The halide system will definitely give me the light I want, but it might be overkill and twice the cost to run. My tank is only 18" tall btw. I'm not considering LED's at the moment because of cost, and I simply don't fully understand the technology.



Can anyone with experience weigh in on this and help me go one way or the other?



THANKS!!!