Both cornstarch and flour can be used to thicken sauces, but they are slightly different. Cornstarch is a more powerful thickener when compared to flour and is also gluten-free, making it a good option for those with dietary restrictions. On the other hand, flour produces a thicker and more opaque sauce, and it adds a subtle flavor to the dish. Ultimately, the choice between cornstarch and flour depends on your personal preference and how thick you want the sauce.