Blueberry muffins tend to be moist and tender, similar to a pound cake, whereas cupcakes are intentionally light and airy. Cupcakes also tend to be sweeter and topped with frosting or a glaze. Muffins may contain a crumble topping but are often served without any extra garnish. Since muffins aren't quite as sweet, they're usually served at breakfast or brunch while cupcakes are treated more like a regular slice of cake and served as dessert.