@UncleB wrote:For me personally, they're virtually identical, other than Sam's Club will take MasterCard (and other cards) but not Visa, and in a few months Costco will be taking Visa but not MasterCard.
Some folks have reported utility companies that would take one over the other, and I read once that somebody had to get their card changed to the other network because their college would only accept it for tuition (I don't recall which). Also, a few folks who travel to more 'obscure' places in Europe have reported finding merchants who only took MasterCard, but this was out-of-the-ordinary since in Europe generally both are accepted equally.
This being said, to me, for 'practical' purposes they are pretty much the same.
And this is why Uncle here chooses to intelligently diversify his credit cards to avoid situations like this as much as possible! 
Still looking to get my hands on a mastercard, lol. (bbr sucks for rewards -- might get a Citi MC in the far future)
It is true that some European countries are more EC card issuers but acceptance of VI and MC I do find equal. What is not to be confused is Maestro service which is the equivalent to US debit/ATM cards in Europe. Many merchants that do not accept credit cards do accept Postcards and Maestro/ATM cards. Diversification is always recommended because if one network is out of service you still find a card to pay "cashless" 
