Originally Posted by
striknein
I have no experience with moustache bars, but my gut tells me that it's the better setup for mountain bike conversions because of the way they're sized. People tend to buy their mountain bikes a little smaller, so the extended reach of the forward position on the bars is probably going to make for the most comfortable position. The rear sweep also gets you upright for climbing, or riding that odd bit of singletrack.
I'm going to speak out against moustache bars for mountain bike conversions; they tend to be road sized so you need to do a full component swap, and they have a lot of reach, so they can be very uncomfortable on a mountain bike with an already long top tube.
I actually like dirt drops on road, but because they have to be set up so high, you don't really get the aero thing going. I'll disagree with Strik about the hoods though. At least with some bars and setups it's possible to get the hoods usable and in fact quite comfortable. I used an Origin8 Gary bar, which is much shallower and has a shorter drop than the Woodchipper, and the hoods were perfectly usable for me.