It's a good price depending on the condition and quality. Is it a fixture made by a company or a retro fit?
Between the two (MH
&T5) is really a personal preference. With MH
you are going to get a deeper penetration into the tank, meaning higher PAR levels even lower. T5 can output high amounts of light, but dont focus enough to make it very deep. These are obviously very brief overviews. What are the dimensions of your tank and what types of coral are you looking to have?
Personally i would probably get the MH
(assuming they aren't in poor condition) and retro some T5's in later on.