Net energy balance will determine how much muscle is catabolized in any given period of time. But even if we put that notion aside:
-Casein may actually be inferior to whey protein. When taken in large amounts (i.e. a pure casein shake), it forms a significant amount of paracasein that goes undigested and leaves you with a big bathroom trip the following morning.
-The migrating motor complex can override casein agglutination in the stomach.
-Digestion rate studies are very limited, and the one's that we have show that casein digests at a mere 2g per hour faster than whey.
-Combining whey or any whole food protein with the slightest bit of fat, fiber, etc will not only mimic casein as far as amino acid release, but possibly slow down AA release beyond that of casein.
^^None of those points even matter (except the paracasein one) given that "windows" of energy flux really don't make a difference in the grand scheme of things. Net energy balance will determine anabolism vs catabolism; these two processes are ongoing and the "net" change is what determines whether you gain or lose weight/muscle.