Banker role or not?

[Hai Feng Kao]

 mbrowne's javascript DCI example uses the banker role in the TransferMoney example.

 role banker {
        transfer() {
            source.withdraw();
            destination.deposit();
        }
    }

However, in Trygve's book "the Common Sense of Object Oriented Programming" page 20, 

Trygve let TransferMoneySource role initiate the transfer (instead of banker role)

role source {
        transfer() {
          this.withdraw();
          destination.deposit();
        }
}

Which way is preferred by DCI? 

1. a coordinator (i.e., a banker role) to supervise the interaction of objects

2.  let objects "talk" to each other