Whey or casein being beneficial is dependent on one’s needs. If gaining muscle mass at a faster rate is the prime goal, then one must opt for whey protein. On the other hand, if preserving the lean muscle mass with better protein absorption is the priority, then casein should be the option. The basic difference between these two milk proteins is their rate of digestion/ the rate at which these are released. Whey gets digested quickly, whereas casein is released steadily and thereby prevents muscle breakdown that is triggered by vigorous workout sessions.