There seem to exist two different camps of people when it comes to cinnamon rolls and their filling. Some say to use regular granulated sugar, cinnamon, and butter while the opposing view states that one should use cinnamon, brown sugar, and butter. Why would one choose one over the other? What advantages or disadvantages does it bring to the cinnamon roll by adjusting the items within the filling?
What I learned researching this question:
Brown sugar has anywhere from 3.5 - 6.5% molasses depending on whether it is light or dark brown sugar. Molasses is what makes brown sugar brown. Brown sugar has a smaller granule than white sugar.
What all this means to a cinnamon roll filling:
When brown sugar and cinnamon (and butter) are used in the filling, the brown sugar becomes more liquidy and less gritty than white sugar. The flavor is richer and more complex. When I make rugalach or almond rolls, I prefer white sugar, cinnamon and butter for the filling which lets the almonds or walnuts bring the flavor to the pastry. Cinnamon rolls do not usually have nuts so the pastry requires more flavor from the filling ingredients (and the icing, of course!)
Here's the site where I read about brown sugar:
There are no advantages or disadvantages in this case, it's all about personal preference. Brown sugar and butter will turn into a rich, sweet, syrupy ooze. White sugar will stay more granular and have less depth of flavor, but arguably you may taste more cinnamon that way. You can also mix the two, there's no reason you cannot have half brown and half granulated sugar
As a suggestion why not try both and see what you think? Do one half with granulated, and one half with brown and do a blind taste test?
Also as a trick you could put granulated sugar into a food processor and whiz it up to make the grains smaller. Smaller grains means it will dissolve more, so you get a cleaner flavor but a bit of ooziness.