Actually, it's advisable to pay with your Mastercard as much as you can. Since you are using their money, they will get the best rate possible. You don't have to pay extra fees or anything like when changing paper money to another currency.
Hotels, restaurants, and anything big that I buy when in Europe always goes on my CC. I had a VISA card and I never had problems using. Everywhere I went that took CCs took both MC and VI.