Capri or Positano for a day from Sorrento?
The question underneath the question
People asking which is prettier are usually asking what kind of day they want. If the answer involves swimming off a boat, passing under an arch in a rock stack and looking into sea caves, only one of the two can offer it, and that is not a matter of taste. If the answer involves walking down through a town to a beach and eating slowly, Capri will feel like a lot of logistics for the privilege. Whether the Capri version earns its price is argued out honestly on is it worth it.
If you pick Capri
The crossing is 20 to 25 minutes on a hydrofoil at roughly €20 to €30, with departures every 30 to 60 minutes in high season, so the island is an easy day from Sorrento even without a tour. With a tour it becomes five to eight hours of coastline, swim stops and three to four hours in the towns. The realistic shape of both versions is on Capri in one day.
Do not try to do both in one day from Sorrento. I have watched people attempt it and the thing they remember afterwards is the travelling.
Frequently asked questions
Which is better, Capri or Positano?
Capri if you want a day on the water, since an island can be circled by boat. Positano if you want a town, a beach and a slow lunch. They are different days rather than better and worse.
Can I visit Capri and Positano in one day?
You can move between them, but you will spend the day in transit rather than in either place. Pick one and give it the hours.
Is Capri worth it if I have already seen the Amalfi Coast?
Yes, for the sea route: the Faraglioni arch, the grottoes and the swim stops are the part you cannot get from the coast road — the full list is on what to see on Capri.