Well the main difference is that one helps with post-workout nutrition and the other helps during your workout. Creatine basically helps you gain a very small amount of energy by the rentention of more water into your muscle cells which enables you to lift at a higher poundage or for a
higher volume of reps thus promoting growth. Whey protein is one of the fastest digesting proteins you can buy, it's role is basically to be taken directly after a workout so your body can start to synthesise protein within minutes which kicks your body into a higher
anabolic state promoting the faster and more efficient anabolism of any nutrients you ingest, such as carbohydrates and proteins. Take the whey with some dextrose (sugar) post-workout.