Some muffin and cake recipes call for the creaming method (start by creaming softened butter and sugar, continue from there). Others just use vegetable oil to provide the fat for the recipe. I've had variations of both that are tasty, and so would like to know more about what each method accomplishes. How does the resulting cake/muffin/baked good differ depending on the method you use, i.e. oil vs. butter/creaming method?