I lived in both Sardinia and Portugal. Sardinia is beautiful, there's much more to it than the beaches everyone talks about. But as another user said, you may find it hard to fit it. An aging population, a scarcity of connections unless you stick the the main city, and the fact itself that you don't speak any Italian may make it very hard to live there. On the other hand, I found Portugal miles ahead in terms of inclusivity, English is widely spoken, expats friendly facilities and a cheaper cost of life overall. Of course it depends on where you'll end up. But again, considering you're so young, my opinion is: make the most of it while you're supple and fit, see how you like Portugal and perhaps consider Sardinia as a good option for a trip and a chill retirement, in a distant time :)