The CM is responsible for coordinating the crew and passengers and liasing with the Flight Deck in an emergency, as well as taking the lead in a prepared emergency, for example.
Now...some FA's have the personal attributes necessary to pull off being a CM. Others are not so comfortable, nor able, to deal with the role. For that reason, they should not be put into a position where they are not comfortable with controlling BOTH the crew AND passengers.
There's nothing different with regard to operating doors, etc. What is different is the responsibility for managing the greatly increased workload associated with any emergency.
CM's, on a daily basis, do more and need to know more than most FA's give them credit for.