The Euronet (bad) machines outnumber Multibanco machines probably 5:1. The cost to pull euros from a Euronet machine exceeds 25%!, but at least they are up front about it and give you a chance to back out of the transaction.
I have not seen the Multibanco ATMs tell you the total cost, so you are trusting that it is lower.
I used a currency exchange before I left and total cost was under 7%. A cash advance on the CC would probably be less costly than some of the ATMs here.