Jamie,
From my conversion experiences i've seen some cases where the original crew were actually xml based figures that appeared or disappeared with certain aircraft systems like lights, engine start, etc. So these things can get lost during the conversion process. Or maybe they are animated in some way that Mldc can't translate, so they disappear in the process, unless one can restore them with scasm. This is where dp figures can be useful and its usually the reason for using them. Otherwise, its always best having them in the model itself as designed whenever possible. In the vast majority of cases, the modeled crew are suited in proper gear for the model and the nationality involved, whereas with available dp figures the closest match doesn't always look just right. Sometimes even the most suitable figure has to be reworked to make a good fit. Plus, we give up a mount point in the dp to the figure which may or may not impose on loadouts depending on the model and the missions one has in mind for it (i'm sure you're familiar with CFS2's mount point limitation).