Between the two, I would go the T5 route. They don't produce as much heat as MH
and are cheaper to run. As for which fixture? It depends on your budget. I would go for a 6 or 8 bulb. If you are handy at DIY, you could wire up your own fixture for cheap with the same results.
Wet/dry converted into sump with a Bubble Magus NAC7 cone skimmer, MAG7 return, 200 micron filter socks, Vortech MP40w + two returns for flow. Current Sundial T5 + two retro Icecap T5's (6 bulbs),