If you have a card that doesn't charge commission on each transaction in the eurozone (such as SAGA or Nationwide) then that is probably the quickest and costs no more than cash. However some cards are best avoided so use cash - provided you are not travelling at peak times when the queing can be long.
I used to use SANEF liber-t and the bill was paid on my eurozone card but was told than these accounts were being closed for non French residents so I switched to the new SANEF account which is paid by direct debit against my UK bank account. SANEF include a currency trannsaction fee on the monthly account so I now pay more than I used to under the old account
