In this case, definitely Capri.
Sorrento is just a lovely, relaxed village with beautiful scenery.
Capri offers beautiful scenery, too, of course, yet in a much wider variety.
You can do a boat tour to the blue grotto or a tour up the Monte Solaro.
Visit the ruins of the Villa Jovis of Roman emperor Tiberius and the Villa San Michele of Axel Munthe.