i'm far from a math wiz too... but i think the coefficient of friction will be the main factor in the amount work to move said poo and feathers... if one 10 lb object in a bag is sitting on 60 grit sandpaper, and the other 10 lb object is in the same bag on a surface covered in silicone, it should require less work to move the one on the silicone.
i have no idea if that applies to wheels tho.
everything changes when you're going through the trails at the speed of light!