I didn't reply straight away, because I didn't want to say anything stupid.
Well, I think that Paul O'Connell is the right Captain, because:
1. His recent form is so good, that there is no issue about him being in the test side.
2. Teams always seem to be best led from the front. Although the glory boys in the Backs do most of the scoring, the forwards dictate the shape and pace of the game. For every "match winning" drop goal, there was a pack of Forwards winning the ball, and giving the Fly Half enough time and space to make the kick.
3. The "changing room door" argument ... this is soooo important. Even in a game like Netball, when the opposition stand and face your Captain, you want them to think "Oh my god, the other side's team leader is Superwoman". In rugby, your Captain should be someone like Martin Johnson, or the French guy ... it'll come to me in a minute ... played for Toullouse, oh god, oh yes ... Fabian Peloux, that's it. Or ... Paul O'Connell.