Bourbon is generally associated with a sweeter profile due to its production process and the ingredients used. By law, bourbon must contain at least 51% corn in its mash bill, and corn contributes a natural sweetness to the whiskey. Additionally, bourbon is often aged in new charred oak barrels, which caramelizes the sugars in the wood and enhances the sweet flavors that develop during the aging process. These factors result in tasting notes such as vanilla, caramel, and toffee, which are characteristic of bourbon.
While Irish whiskey tends to be smooth and light, and Tennessee whiskey shares some similarities with bourbon, they do not typically have the same level of sweetness that bourbon does. Scotch whisky, especially those that are peated, can have a smoky profile that is quite different and usually does not emphasize sweetness to the same degree.