Light brown sugar is the more popular of the two, and it's what you'll often find in most cookie recipes. It's made by adding a small amount of molasses to refined white sugar, giving it a slightly caramel-like flavor. This is the perfect choice for those who like their cookies on the sweeter side.
In contrast, dark brown sugar has a richer, deeper flavor that's more pronounced and less sweet. This is because it contains a higher percentage of molasses, which gives it a more complex taste profile. If you're the type of person who loves a good chocolate chip cookie, dark brown sugar might just become your new best friend.