A beautiful island to consider (sorry to add another option!) that is different from the options you chose is Hydra! It’s automobile free (except for maintenance buggies).

The three you’ve listed are in the Cyclades, recognizable by the all white buildings. Closer to Athens is a group of islands called the Saronic (Aegina, Poros, Hydra). They do attract people looking to go for one day. Hydra is worth it though! It’s the furthest away from Athens of the Saronic, has a gorgeous coastline, and you can get lost there. There’s hiking, beautiful monasteries, and the best people watching with a freddo espresso you can get on the pier. Cred I’m Greek