A few commenters have argued that Visa charges more for foreign currency conversion than MasterCard — that a Visa with ‘no foreign currency conversion fees’ isn’t really because Visa marks up their exchange rate by 1%.
I’m testing this out on a few trips. I mentioned in the comments that I’m experimenting with comparisons, and I’ve had a couple of folks ask about the status of this in the comments and also by email, so I thought I’d provide an update.