Positano/Amalfi coast by car or ferry??

Ferry
Get off for a quick stop in Positano
Then continue to Amalfi and take the bus up to Ravello

We hired a driver although it was early October for us. We loved our trip, the driver knew exactly where and when he was going, knew when the big tour buses were coming and called ahead for parking.

He was able to recommend beautiful spots for photos, lunch and wine.

I am sure the ferries would be good too, but don't discount the experience with a driver who knows the area. We stopped in Positano first, then an extended stop in Ravello for lunch, then Amalfi for a glass of wine in the square. Lots of little stops in between to look at the amazing ceramics and pottery.

I definitely agree with DebH. Hiring an experienced driver is a must. Below is the link for who we used. We saw a ton of people waiting for the bus's in Ravello---not my idea of a enjoyable day. You only have one day and you are talking the beginning of Sept ( it probably will be really hot). It would be great to see by ferry but you don't have the time. Enjoy! The coast is stunning---too bad you can't actually stay for a night or 2 but definitely a driver will make for a wonderful day.

https://www.topexcursionsorrento.com/

We chose, a last week in May, to hire a car and driver for eight hours from Sorrento. (Couple of hundred Euros.) That can be convenient for four people, but it also depends on whether getting to a certain number of very specific places is important to you. I don't mean for it to sound so negative, but you need to consider some of the "cons" to the "exotic romance of the boat in this magical place:" (When the driver (not a professional tour guide) asked us about "the pottery store", I had the presence of mind to answer, "Wow, do they have a line of bathrooms for visitors? We'll do that, and skip the pottery.")

Americans returning to school are not the only patrons of this area. September will not be deserted
The ferries are not as frequent as busses, so it's not a hop-on-hop-off touring situation.
Positano's dock can only accept smaller ferry boats. (Capacity and water-roughness)
Make sure you have the right ferry schedule for your dates.
Positano has hundreds of stairs for a comprehensive visit on foot.
Ravello is a long way from Sorrento, if a "must-see."
Infrastructure and public transit can be unreliable in Southern Italy.

https://community.ricksteves.com/travel-forum/italy/amalfi-coast-september-transportation-issues

https://community.ricksteves.com/travel-forum/trip-reports/trip-report-2-weeks-of-day-trips-from-sorrento

https://community.ricksteves.com/travel-forum/italy/getting-around-amalfi-coast

https://community.ricksteves.com/travel-forum/italy/amalfi-coast-day-trip

Definitely ferry! The views of the coastline are just incredible.

Thank you everyone. It's a tough decision for me, unfortunately we have one day. We are visiting Capri and Pompeii on two other days. I'm feeling that if we're on the water to Capri then doing a land / driver tour of the coast would be good.
If we did the ferry to Positano and Amalfi, then we would have to deal with taking a bus to Ravello which I hear can be very crowded so I'm guessing we would skip ravello and just see areas that are walkable near the port? To take the ferry back to Sorrento; is it something we can just hop on or does it need to be scheduled in advance? I wouldn't know our timing until that day.

I would feel better if we had more precise information on crowd levels in September, but in the first week of September, I would still expect the AC to be jammed. Here is one version of the ferry schedules. But more research needs to be done on the last day of this (multiple actual companies) schedule. I'm suggesting you look for the primary sources of the schedules and not just this TI compilation. I myself would buy the return ticket when leaving Sorrento, if not before. Note how early the last ferries are.

https://www.ravello.com/ferry-schedule/sorrento/amalfi/

While it is small, Ravello is an absolute favorite of many posters. I understand your impulse to skip it, but I would skim over Amalfi instead. Opinion. You need to factor in the uncertainties of southern Italy, like checking the SITA bus schedule as a backup for a cancelled ferry. And holding taxi money in reserve.

Great info from everyone. Thank you! I am leaning towards a private tour guide/driver for this day. Sounds like the best option to me.