Month of the year? Air conditioning is essential for much of the year. Another reason it matters is that Positano can only take smaller ferries. There are in-season, and off-season ferry schedules, and occasional cancellations for high seas. Many more ferries in Sorrento. What time is the Naples flight out? It is almost certain that you will need a 120 Euro car service for that, if it's late enough to be safe from Positano. And a Mercedes sedan is tight for four passengers. Do not underestimate Positano's disconnection from both Sorrento and Salerno (another place with trains.) Also be aware that the Circumvesuviana train from Naples to Sorrento can be hot, crowded, and gritty, with annoying accordion players demanding tips. Many people use a car service to avoid this train. We rode it inbound, and put a car service on our Sorrento hotel bill, for departure. That was an easy decision because we paid 15 Euros for a very short cab ride within Sorrento! Hotel had a local surface travel provider, so we were confident of good service.
While Sorrento is generally, a post-war, purpose-built, reinforced-concrete resort town, it has superb transit connections, particularly for Naples, Pompeii, Herculaneum, Capri. It also has two modest-sized ports (and some ferry horn noise at times.) It has about five large luxury hotels (where you could take one room with a huge extra-cost balcony, and one cheaper room.) Elevator in hotel goes to a private boardwalk (NO beach) swimming platform, with bar, in the Gulf. And many other medium and small hotels. We stayed at the Ambasciatori, a worthwhile splurge. At the time, one company ran the five big cliffside hotels, but they had separate identities.
It is not true that there are no budget hotels in Positano. But it is historically a luxury resort, with several hotels around $1,000 a day. Perhaps the most famous is La Sireneuse, where we had a drink, just to get a look. The private hotel pool was about 8' by 20', and everyone lounging there appeared (to me, not a doctor) to have had "work done." We could not sit by the pool because we were not guests. The water view was partial and indirect. I found the same euro-boutiques lining the pedestrian streets to be the same brands you see on Capri, in Rome, and in Paris.
As noted, some hotels are hundreds (read that again ... ) of steps up from the ONLY two-lane road through Positano. The beaches are all pebbles, and quite busy in season. Capri is also highly pedestrianized, and you should get clear information from your Capri hotel about luggage transfer from the Capri port-which might have a 1/4 mile walk from the boat to the funicular.
I'm not trying to be negative. We enjoyed our two DAY trips to Capri (one on a cruise), and were glad we stayed in Sorrento, even though we didn't post on Trip Advisor Sorrento "Eyyy, 'ow much is a Pint?". We happily skipped the Blue Grotto on our Capri day, and were sorry it was too far from Sorrento for the UNESCO WHS Paestum temples.
Edit: Sorrento has precisely one, very small, sand beach, which is located directly between the two marinas. So it has a distinct odor of diesel fuel. It's actually easy to get to, because there is a 2 Euro elevator from there to one of the town squares. The town is on a sheer cliff, with lovely views, including Vesuvius.