Dutch processed has been Alkalized to offset the natural acidity of cocoa solids, which can be bitter. Its darker, more smoove and rich, generally better IMHO.
Natural cocoa has the tendency to screw up any recipe that calls for for baking soda (alkaline) because of its nearly neutral pH, so you have to use dutch processed with baking powder unless you add a pretty serious acidifyer.
SO..... if the recipe says 'use Dutch Processed Cocoa powder' , you should use it or you will mess with the levening agent pH ratio ballance, they are not just being fancy schmancy, it really does matter.