I have not been to Sardinia (yet! it's high on my list), but I have read numerous times that it has the finest beaches in the Mediterranean, the only ones comparable to the Caribbean is a quote I recall. Croatia's beaches are mostly pebble or rock, so while I like the clarity of the water that produces, that may not be what you are seeking. Find out more at http://www.croatia-beaches.com/.
There are not many 4-5 star beach resorts in Croatia, that is one way they have brilliantly preserved the charm of the coast. It is quite common to rent your own apartment.
If I were you, I would let the flights determine my choice, in order to maximize the 7 days. enjoy!

I haven't been to Sardinia but have the impression it's mostly a beach/relaxation destination. Whereas with a little travel (especially by boat) there are more sights and scenery to be seen in Croatia. (But also plenty of relaxation.) Split has a biggish airport, Dubrovnik a smaller one.

So it depends on how you want to spend your week. If you want more information on what's to be seen in Croatia, just ask.

Hi...

I have not been on a rocky/pebbly beach since I was in southern France with my parents years ago so please excuse my naive questions that follow.

Do the rocks/pebbles continue into the water? Are sharp rocks a problem as you walk into the water? Where do the rocks end and the sand begin?


Now for the more intelligent questions:

Is 7 days enough to visit sites in Croatia and have time for relaxation at a beach? Are there any nice resorts on a beach close to interesting places? We enjoy walking around medieval towns, especially in the evening so we would need some recommendations as to where to base ourselves. We can land at Split or Dubrovnik.

Thanks again.

Andrea

No worries--I am from the southeastern US, so I was unfamiliar with non-sandy beaches until my first visit to Croatia.
There is no sand, the rock extends into the water. However, there is a big difference between a rock beach (sometimes called a shingle beach) and a pebble beach. Unless you are the most tender of the tender-footed, you can walk barefoot on a pebble beach, as they are worn smooth. You may still want water shoes (sold in every town if you don't bring your own) because this is sea urchin habitat. On the public or otherwise popular beaches, the urchins have been removed in most cases, but if you want to explore a bit and find your own private cove, which I highly recommend, then you are likely to find urchins and you don't want a spine in your foot.
At the shingle beaches, there is usually a ladder installed. These are a bit wilder, and my preference when the sea is cold and I just want to sit and stare. The sea is usually deeper offshore from these.
There are some sandy beaches in Croatia, but they often require a boat to get to. The one I have been to, at Lumbarda on Korcula, was unimpressive to me, as the sand was dark and the seaweed plentiful.
Hope that helps--the rock issue is no reason to avoid the beaches in Croatia, as they are quite stunning with clear seas, but you want to know what you are getting of course.
That Croatia beaches site is comprehensive, so I advise perusing it.
With 7 days, you would have plenty of time for a lovely visit. You could fly into Split and enjoy its environs (Trogir, the islands of Hvar, Brac, Vis); or fly into Dubrovnik and visit the nearby Elafiti islands, plus Mljet and Korcula; OR you could fly into one and out the other and choose from many options. They are 4 hours apart by bus/car, but if you want to see some of both areas then flying open jaw is best. You really can't go wrong.
I'd stay in the town for both Dubrovnik and Split/Trogir, as well as the main island towns of Korcula, Hvar, and Vis. While on the islands you can easily get to beaches. You can also find villas or apartments in more rural settings if you wish to rent a car. All up to you.

You all make Croatia sound appealing as a destination, but I have heard so many nice things about Sardinia. As well, I once saw a one hour long travel special on Sardinia and fell in love with what I saw. I am sure both are beautiful, but I would also love to hear what people have to say about Sardinia.

I will be flying into the southern part of Sardinia (Cagliari) if I choose to go there, and I am not sure if that would have an impact on my choice.


Thanks


Andrea

I've been several times to Sardinia, always off season as July and August are hectic and very crowded. It is absolutely beautiful and there is much more to it than beaches (though they are exceptional). You may be interested to read my trip reports :
http://www.fodors.com/community/europe/alghero-and-area-trip-report-sardinia.cfm?6
http://www.fodors.com/community/europe/a-week-in-cagliari-and-around---march-4-to-11.cfm?12
http://www.fodors.com/community/europe/sardinia-again.cfm?11

Andrea, the southern part of Sardinia is absolutely beautiful . Sardinia is not just beaches , as Mimar said, but a land full of history.Sardinia is one of the most geologically ancient bodies of land in Europe. You can relax of course on white sandy beaches but you can also visit the remains of a prehistoric Nuraghe village or caves, mines... Don't forget to taste the local gastronomy!!!