Expensive aged balsamic can be almost syrup-like and have deep, rich flavor. Use aged balsamic vinegar to drizzle on a dish at the very end. This recipe for Strawberries with Buttermilk Ice and Balsamic Vinegar is a great example of how to use aged balsamic.
Use regular grocery store brands of balsamic vinegar when it is an ingredient, as in a salad dressing. The Cranberry Vinaigrette recipe in the photo above is an example of using balsamic as an ingredient.
Think of the aged balsamic as a truffle, and the ordinary balsamic as a white button mushroom—you want both in your kitchen, but they have very different uses.