In order to avoid the commission on the exchange rate I opened an ING Everyday account and use its debit card to withdraw money from ATM machines in Spain. ING do not charge any ATM fees and use the daily international mastercard exchange rate - whatever that happens to be. So no commission or markup.
Also any withdrawal fees charged by the operator of the ATM machine will be rebated by ING.
I used to use a Commonwealth Bank Money Card (a multi-currency debit card) but the downside was the commission on the exchange rate, and usually a charge by the operator of the ATM machine.
I also have a 28 Degree Mastercard credit card for the few places that take credit cards - large hotels! It also has no commission or mark-up on the exchange rate and is cost effective as long as you only use it for purchases (not cash withdrawals) and pay it off within the interest free period - like all true credit cards the interest rates are ruinous.
ATMs are common, so, provided you have the ability to withdraw money from a debit card, there is no need to carry large amounts of cash.
A few years ago Choice (Australian Consumers Association) did run a comparison on travel money cards, but it is probably out of date now.