"Smartest" way depends on your circumstances, which bank you use, your money needs, etc. "Smartest" way for one person does not necessary mean "Smartest" way for you.

Here are some more considerations that can change the equation.

Credit cards: The gotchas here are DCC, rates, fraud protection, card swiping, and smartchip.

Dynamic Currency Conversion. This is a scheme whereby the cc processing machine proposes to do you a "favor" by charging you in your home country currency. Using what exchange rate? Of course, at the rate favorable to them and rip-off for you. When you detect this, you are to cry foul and demand to be charged in local currency.

Rates. Here are components are 1% charged by Visa/MC, another 1-2% "profit" charged by your bank. More % get tacked on, less attractive that cc gets.

Fraud protection. Some CC companies use paranoid fraud protection services. I have one such card. They think any oversea purchase over $500 is an automatic fraud and make me call them every time this happens to unlock the card. Unless you are also this paranoid, you don't want to use such card.

Card swiping. This is nothing special, but the consequence is more annoying while traveling. This is when an unscrupulous employee that takes your card away uses the card for payments other than you authorized, usually a lot more causing you to hit the credit limit or get the card frozen. You can eventually untangle this, but it is a hassle abroad. Try to use the card only where you can see your card all the time.

Smartchip. If your CC is swipe only type, your card will not work on machines that require a smartchip. This is usually an issue at unattended vending machines especially in France.

I never get Euros ahead of time but instead go to one of the many ATM's at the airport. Last year we arrived in London on Easter Sunday. We tried six ATM's at the airport and not one of them was functioning. We were in a
panic because our limo driver was waiting to take us to our hotel and he required cash. Thankfully, he took pity on us and drove into London where he found a functioning ATM.

The upshot of all this is from now on I will take at least 100 Euros with me.

Pick up Euros at the European airport. Tell you credit card company that you are going abroad and confirm they have understood where that is. Take a credit card and push most of it on that but also take a debit card because some companies will not accept credit cards (not many but I had this problem on Saturday in Germany). Leave in your wallet some dollars in two forms. 50s and 1s. In the worst situation a $1 can act as a tip if you have run out of cash in one of those weird moments (eg Damascus airport at 2 in the morning and you need the loo)