A question about currency exchanges.

Hi there.

I am a 19 year old citizen of Iceland and I am currently working in Denmark this summer. In August however, my girlfriend and I are going to Spain, with a quick stop in Iceland. So there we have 3 different currencies, the euro, danish krona(DKK) and icelandic krona(which sucks btw ). We have a bank account in Iceland and Denmark and we were wondering what path is the most profitable for us to go down.

She thinks that changing the DKK to ISK and using our Icelandic debit cards in Spain will mean a loss of value in our money. She also thinks that using our Danish debit card in Spain will be more profitable. So my question is, is that really so?

Is there any significant loss of value by using an Icelandic debit card in Spain rather than using a Danish one?