Many people think the AMEX blue is a [broken link removed]. It is, in fact, a credit card.
If you switch a card during the year and close the original card you will only pay €40 stamp duty. If you hold onto the 2 credit cards you will pay €80 in stamp duty.
Many people, myself included, have Amex Blue cards. I use it to pay for most items - groceries, petrol, insurance, flights, etc. However, it is not accepted everywhere and so I do not rely on it as my only credit card. The cash back which I receive from Amex pays the stamp duty on my cards and also gives me some pocket money for myself.
Marion