I agree, find out what works best for you
But if I can throw in my two cents :
T5's are better for odd shaped tanks (like bowfronts) where MH are better for boxes. T5's give more even light distribution to reach all corners of the tanks where as a MH will give you a spotlight.
I'm assuming your tank is 3' wide so I just did some really quick cost calculations using J&L -
Tek T5
36" 4 bulb unit $300 x (4) $25/bulb = Total $400
36" 6 bulb unit $380 x (6) $25/bulb = $530
Coralife 25W MH w/PC sup.
36" Unit w/bulbs $654
This is about the cheapest MH unit you can get unless you want a single pendant with no actinics but that is still going to run you ~ $400 (canopy/bulb/ballast)
IMHO T5's are a superior light at a much better price point.. pluss you get the flexibilty of exactly tuning your colour using different bulb configs where you are stuck with maybe 3 realistic MH bulb choices and three colours.
The only thing that is a visual draw back to T5 is that the the tank does look a little flat without the shimmer of MH, but having PC's right now you would not get that anyways