Should I use light or dark brown sugar?

Why you should always pack brown sugar when measuring | completelydelicious.com

The difference between light and dark brown sugar is the amount of molasses that’s been added to the sugar. Light brown sugar is subtle, while dark brown sugar has a more intense molasses flavor. You can use them interchangeably in any recipe that calls for brown sugar, per your preference. I always bake with dark brown sugar as I like the additional punch of flavor.