Hi Graham
We've only been to Parga once but absolutely loved it and will definitely go back. We have been to Samos twice (last time 10 years ago) but stayed just outside Pythagorian at Potokaki. We did drive over to Kokkari but chose a very dull day and it didn't look the least bit appealing. I can't really give you much of an opinion except to say that Kokkari was not a patch on Parga as it was nowhere near as beautiful or scenic. Samos itself however is a lovely island it's full of history has loads of ruins and the people are extremely friendly. There are just 2 sandy beaches both called Psilli Ammos at either end of the Island and most of the rest are pebbles apart from Kambos which is sand and shingle (though that wasn't even a resort when we were there!)
Because of its close proximity to Turkey it has military bases around every corner and we saw soldiers out and about all the time but that wasn't a problem. It's also very windy and has wind farms which we've never come across anywhere else.
We haven't been back to Samos because we have a little boy now and children and pebbles really don't go well together! But we fell in love with the place and would like to return one day.
Hope this helps a bit
Diane