Light and Dark Brown Sugar

I made the Outrageous Chocolate Cookies this weekend (I didn't name them, I promise) and the recipe calls for light brown sugar. All I had was dark. Had I known, I might have tried an exciting switcheroo to make the dark sugar light, but instead I just proceeded with a simple substitution, to no adverse effects that I could see. So, what's the diff? Why specifically call for light brown sugar when both light and dark yield similarly outrageous results? Chris speculated that it might have to do with the color of the cookies, but I think he said that without thinking because surely, at least in this recipe, the immense amount of chocolate put into the batter would camouflage any difference in color. The Internets doesn't seem definitive on this. I found out that dark brown sugar, with more molasses, has a bigger flavor and is, of course, darker, but I was wondering if it also had more moisture (which is important to consider in baked goods, eh?). Unclear. Thoughts?

By the way, my friend Jean from high school might be posting some recipes here, too. She makes killer salads, which is definitely an area in which I am lacking.