MSE and a few other sites made FX comparisons between Visa and Mastercard. The FX pairs compared did not include EUR/GBP which is for us UK travellers to EU mainland more relevant than USD.
I crunched a few numbers and am happy to report that on the basis of a small sample (June 2018) Mastercard was indeed giving better rates.
What I found was this:
(1) Both Visa and Mastercard were converting EUR transactions close to the daily high of the spot exchange rate. While Visa was in fact 1.2 pts (= 0.00012) above the spot rate Mastercard stayed below (0.000182 below the high). Visa converting marginally outside the daily wholesale trading range does tick me off a little.
(2) Both CC providers used Friday’s high to convert all transactions over the weekend that followed.
(3) Mastercard did indeed perform better than Visa. Their rates were 0.000262 better than Visa during June.
Data: I used Reuters for daily interbank/wholesale rates, Visa and Mastercard rates taken from their websites.
Overall, 2.62 pts difference should rarely make a difference for small amounts due to rounding, but when paying larger ones such as for the hotel, Mastercard would have had a marginal edge. For corporate/frequent travellers this might be of interest as well. But shopping around to get a sharp deal for the trip outways by far any FX conversion differences.