What they said. Many credit cards say things like (Capital One)
You may be unable to receive benefits in Australia, Italy, or New Zealand. Please contact your vehicle rental agency before you travel.
Amex:
Coverage is not available for cars rented in Australia, Ireland, Israel, Italy, Jamaica and New Zealand.
So no matter which you choose, make sure you are covered there.
Three days for what you are planning by the way seems way too aggressive, make sure you leave plenty of time to enjoy what I believe is the one of the most beautiful areas on the planet.