Another case where DCC could theoretically benefit the cardholder is in the situation where the cardholder's bank does not charge a foreign transaction charge for purchases made in the card's native currency. This was mostly the case in the US until 10-15 years ago: back then, the common 3% charge was stated as being for foreign currency conversion. Then, most (or at least many) banks changed it to be a "foreign transaction fee" that was assessed even if the charge was made in USD.

For situations where the issuing bank only charges extra for currency conversion, then the argument could be made that DCC gives the consumer "more choice" as they can choose to have either the merchant or their own bank do the currency conversion. In practice, I suspect that the typical DCC rate is far more than 3%.