The same weight of brown and white sugars has the same sweetness. Because white sugar is denser than brown sugar, to get equal sweetness firmly pack the brown sugar so when inverted the cup of brown sugar will hold its shape.
Substituting brown sugar for white sugar in a recipe will produce a baked good that is a little moister with a slight butterscotch flavor.
Brown sugar has a slightly lower caloric value by mass than white sugar due to the presence of water. Brown sugar has been touted as having health benefits ranging from soothing menstrual cramps to serving as an anti-aging skin treatment.