You're giving too much importante to an armband. A talkative guy will be talkative with/out an armband and a quiet guy will be quiet with/out it. Maybe in the past being a captain would make more sense, because the captain was suppose to be the only to talk to the referee (at least in Brazil it was like that).
Nowadays pretty much every player talks to their teammates and express feelings during a game. And probably everyone in the team knows who's the guy to look when things get tough. When Puyol was the captain commanding the team, if you gave the armband to anyone in Pep's team wouldn't change anything because he was the guy leading the team, telling other players what to do/where to go. Messi still would be the man to give the ball in difficult games.
Another example is that Messi is the captain in Argentina but he's not the moral leader, he's the technical leader, so Mascherano is the guy giving orders. Switch the armband to Masch and he will still be the guy telling people what to do and Messi will be still the technical leader.