Look Rafa took the armband off hyypia unfairly and handed to gerrard.
My view is:
a) the senior players should all be standing up and leading. its a group thing.
b) the captain should be the extension of the coaches into the squad. he should in theory be giving feedback to coaches on feelings in dressing room etc. A players representative. If our club doens't need one and they can all talk openly so much the better
c) the captain is an external representation of the club to the world. he is the one who will be speaking in public or on tour etc. its a media thing
so: on the pitch... theres no role of captain bar hand over a pennant and see the ref toss a coin. Off the pitch it depends on the group of players and manager, the days of senior men meeting in a room and deciding what to do as players should be long gone but it still happens to get a manager the sack. The captain job is to bring along the guys who are not buying in. peer pressure etc.
I wouldn't think henderson is all that as a captain but who knows. I wouldn't have rated gerrard as one par se.