Well considering I have yet to try either in a planted tank I can only give an opinion based on what I've seen or have read. They both have their pros and cons:
Cost:
Initial cost may seem more with some MH setups but if you are willing to do a little DIY, MH is actually equivalent to CF. If you run an electronic ballast then MH will cost you less in the long run and you only have to change two bulbs rather than 6 each time.
Look:
I like the shimmering look of MH lights and the reflections they create.
Spectrum:
From what I have read, it would seem that MH bubls have a wider spectrum and of superior quality to fluorescent lighting.
Positioning:
In a closed hood, both are going to cause plenty of heat, the MH bulb will be more concentrated however and I found that out just the other day when I burned the top of a canopy I'm building for a reef tank. If open tanks are anything that inspire you, then pendant MH is the way to go.
Last, SE or DE? This is where I'd favor the SE (single end bulbs) personally. First of all there is more to choose from in the US, second they don't require a UV shield and therefore are a safer choice for the DIY'er. If you choose the right ballast, for example the Blueline e-ballast, you can always change lamp holder from SE to DE or the other way around if you ever change your mind. DE bulbs on the other hand are smaller and will make for a nicer more compact pendant but it does require a UV shield.
Hope that helps, it's not an easy choice but rarely will you hear of someone using MH wishing they had purchased fluorescents instead.
Giancarlo Podio | 
Linear Mode
