The S-Class S650 is more powerful as it is equipped with a 5980 cc petrol engine and the S560 is equipped with a 3982 cc petrol engine. There are many features offered in S650 that are absent in the S560. For a detailed comparison, follow the below link - Compare. Moreover, you may have a test drive of the cars for a better idea of comfort and drive quality by visiting the nearest dealer in your city. You can click on the following link to see the details of the nearest dealership and selecting your city accordingly - Dealers.