town of Amalfi or Sorrento

Hands down Sorrento. Loved it there.

It would depend on where else the tour goes and if this is an overnight or more than one night or just a stop for the day.

If you won't see the Amalfi Coast unless you stop in Amalfi, then I'd do that. As a town Sorrento is much nicer. But from Amalfi you can take a bus up to Ravello which is supposed to be much better than either - sadly I didn't get there :-(

Hands way down, Sorrento!!!!!!!

On tour I am also going to Pompeii and Positano.

It is not clear at all if you are talking about overnight stops or just part of a day trip excursion?

The fact you mention Positano and Pompeii on this same tour makes things even more confusing to me.

From Sorrento to Positano you will see some of the Amalfi Coast. Sorrento is well-positioned for going to Pompeii. It makes a great base.

If you have time, though, try to make it all the way to Amalfi Town and up to Ravello. That will be a full day by bus.

This is a full day private shore excursion I am going on. Just wandering if Sorrento is better to see or rather see more of the Amalfi coast on the way to Amalfi from Positano. Pompeii is also a stop for a 2 hour guided tour. Whole tour will be 8-9 hours from the port of Naples.

Do realize many responses above likely thought you were asking where should you stay overnight for multiple nights of your 2 choices.

9 hours including Pompeii and Amalfi is far from ideal, I assume you realize that.

Of your choices Amalfi for me most definitely, though, as others mentioned if you can quickly walk Amalfi town and then take the local SITA bus to see Ravello for a couple of hours ; that would be even better.
The ride from Positano to Amalfi is very scenic and think for a couple of hours as part of a day trip you would enjoy that more than Sorrento.

Sorrento has more to see because of its size.

However, Amalfi and Ravello, which is a quick bus ride up the hill, has spectacular scenery and iconic views.

I am not sure if you are with a cruise tour guide, but one could hike down from Ravello into Maori for another delightful view.

Let me start by saying that you cannot make a bad choice here. You'll enjoy whichever third stop you choose.

Of your 8-9 hour excursion, there's 2 hours at Pompeii and bus time could be close to 3 hours, so you'll be left with 3-4 hours for the other 2 stops. Not sure whether that would allow enough time to visit Ravello by local bus, which is one of the pluses to choosing Amalfi. Another consideration is that Amalfi is small and I can envision its few sights being very crowded when multiple busloads of people arrive at about the same time. Sorrento is much larger and can better absorb the influx. Depending on where the excursion will be at lunch hour, you'll find far more lunch choices in Sorrento than in Amalfi. Both towns are different enough from Positano to make a visit worthwhile, so weigh everyone's feedback and pick whichever one most appeals to you.

Given your time limitations, I would suggest Sorrento. Cuts down on your 'time in transit', and I can affirm what others have said, Sorrento is Fabulous.

Sorrento is beautiful as well as Amalfi.

Sorrento is bigger and well located to visit Pompeii and Napoli. However, if you want to see/feel the Amalfi Coast, then Amalfi.
You can stay in Praiano, take the bus visit Ravello, Amalfi, Positano, and a bunch of other little towns around the Costiliera Amalfitana.

Amalfi reminds me of Myrtle beach , very touristy. Sorrento by far us better but we stayed in a villa in Ravello and that was special. Positano is superb