Yes, it is totally worth it, especially since Madeira beaches are mostly rocky or volcanic black sand. Porto Santo has an incredible 9-kilometer stretch of golden sand with therapeutic properties, and the water feels a bit warmer too. A day trip using the morning ferry is fine, but staying one night is much better so you can enjoy the quiet evening vibe after the day-trippers leave. Besides the beach, you can rent a scooter or a small electric car to see some cool volcanic rock formations, hike up Pico do Ana Ferreira, and check out viewpoints like Miradouro das Flores. There is a helpful
https://guidekin.com/journal/porto-santo-madeira-gu... that breaks down the ferry schedule, hotel options, and things to see there. It is a very relaxing and peaceful place, totally different from the main island.