A typical T5 with single light reflectors will produce more light per watt than a typical MH setup. This is a constant debate in the reef community (I think because the MH people dont want to admint flourscent has come a long way), but there have been many people that have done meaurements between T5 and MH. The result is T5 produces as much light or sometimes more than MH.

With the right mix of bulbs you should be able to get the same spectrum with T5s with much longer bulb life.

Reef Central Online Community - T5 PAR not as good as we thought?

That link is 1 such comparison and if you scroll to the bottom and look a the pictures, the T5 234 (6x39) watt setup has more light reaching the bottom of the tank then the 250 watt MH.