If my knowledge is correct with respect to simple SSL, Mutually Authenticated-SSL has the advantage that both end parts are authenticated one to another:
Not only the Client endpoint knows that he is communicating with the Authenticated Server endpoint, but also the Server endpoint is sure that he is communicating data with Authenticated Client endpoint and not with a third party unauthorized (MITM).
My question is:
"In what kind of scenario will this grant a higher level of security in communication?"
In other terms:
"What kind of attack that a MITM can pursue in a communication based on simple SSL is completely avoided with MA-SSL?"