Scenery
Pretty, low-key
Dramatic caldera views
Santorini's volcanic caldera has no real equivalent elsewhere in the Cyclades.
Price level
Moderate
High, especially caldera-view stays
Caldera-facing hotels in Santorini are among the most expensive in Greece.
Crowds
Busy in August, calmer otherwise
Very busy, including cruise day-trips
Fira and Oia see cruise-ship crowds that Paros simply doesn't get.
Beach time
Long sandy and windsurf beaches
Volcanic sand, fewer standout beaches
If beach days matter most, Paros usually delivers more of them.
Evenings
Naoussa's harbor bars and tavernas
Sunset crowds, caldera-view dining
Different kind of evening: a lively harbor town versus a sunset spectacle.