I just had a recent purchase using VISA €30 converted to $33.26 when posted on 6/28/16 which corresponds exactly (within the penny) to VISA posted conversion rate of 1.108689 for that date. BankAmericard Travel Rewards VISA.
The MasterCard published rate for EUR to USD for that same posting date is 1.110700. Certainly not better. Just a hair worse - it would have cost me 6 cents more.
Don't understand what the fuss is all about.
I know it's just one example. But there has been quite a bit of EUR/USD volatility lately. If the transaction had posted over the weekend, the conversion rate would not have been as good. See below.
I do notice that if the transaction had posted on 6/27/16 instead, the VISA rate would have been worse - 1.136462 versus 1.108000 for MasterCard. The Friday prior (day after Brexit vote) had a big swing in the exchange rates, and Friday established Monday's rate for VISA. Whereas MasterCard clearly used some other criteria for its rate. So perhaps it's days with a lot of currency volatility where MasterCard is better than VISA.
https://usa.visa.com/support/consume...lculator.html/
https://www.mastercard.com/global/currencyconversion/