It's what you feel. If a sub feels saying Sir, Mama, Mistress, Master, etc: work for them they should. However, a dominant should require how they are to be addressed, and a sub should respond approipriately. You can talk to me by MY first name, but not if you are MY sub. It's about the DOM and the sub. Think about it little lady.
OK, You aren't a little lady. MY point is subs and Dominants.