Generally, I think that it is best if the captain is a player who plays the full 80 minutes. Often, the importance of the captain comes into focus during the last 15 minutes of the game.
For this reason, I am generally not in favour of the captain coming from front row or the half backs as these are commonly subbed at around 60 minutes.

Oh you poor Northern chaps. Just use one of your solid gold cigarette cases, surely?

And they say Quins are the champagne Charlies of rugby. 🙄