The fluorescents will do you if (1) you can mount them really low (2) you keep the water really clean by using the methods of overfiltration, UV, activated charcoal, etc (3) you keep the glass clean, and (4) you don't have a lot of canopy type plant growth.
There are those that say water depth doesn't affect intensity, but that is only true if the above conditions are met (low lights and clean water and glass).
When I ran MH over a 20 g, I mounted a fan ($7-$10) in the diy wood canopy and wired it with the lights so both ran at the same time. I didn't have temp probmes with my reef.
It really depends on where you want to go, I might be tempted to try the fluorsecents (see my sig) given the price you found, but you might have to face upgrading if things don't work as you expected. I also like fewer overdriven versus mashing a bunch of tubes in.
I think you'll get as much heat from 8 fluorescents and (4?) ballasts as the MH (the ballasts are mounted remotely). I think wattage is wattage versus costs, but the MH bulbs last longer as I recall (they do cost more, but we're talking 2 versus 8).
75g 3 T8s 2x OD, XP3, pres. CO2,