Herculaneum or Pompeii

I think it depends on how much time you have. They're both great, but Pompeii is larger and takes more time. It may also be more crowded. We probably enjoyed Herculaneum more, the visit feeling more intimate. You won't go wrong with either choice.

Pompeii is the better choice due to size. One can easily spend all day there. However, it is possible to do both in one -- one in the morning and one in the afternoon if you are already in Naples. We've done that. But if you are going there from Rome, it is going to be a loooong day regardless and for that reason I'd opt for Pompeii.

I prefer Herculaneum. Pompeii can be a bit overwhelming and the crowds certainly can be an issue and it is also less preserved than Herculaneum.

Herculaneum is smaller, more manageable and I found the artefacts more interesting due to the better preservation.

When we had the choice, we went with Herculaneum because it was smaller and I felt we could manage a quick visit more easily. We were there in April 2016 - it was largely deserted and we were able to wander freely. We were very happy with our choice and learned a lot.

We stopped at both on the way from Sorrento to Naples this past March. We were somewhat cramped for time since we had to catch an afternoon train in Naples (pre-purchased tickets at a deep discount, so was committed to a specific train). We had a two-hour guided tour in Pompeii and spent about 1.5 hours our own in Herculaneum. Two hours barely scratches the surface of Pompeii, although we did see a number of the highlighted homes and businesses, while you can cover basically all of Herculaneum in 1.5 hours, since it is much smaller. They are very different cities, so if you can catch both it is really worthwhile. We decided to forego Naples entirely except for the train station.

It would be a lo-o-ong daytrip, but if you're real adventuresome (and the weather isn't crappy) I'd try this:

Leave Roma Termini station 8:48 AM, arrive Napoli Centrale 9:55. (~35 Euro/pp)

Take Regionale Circumvesuviana Napoli Centrale 10:07, arrive Pompei 10:42 (~5 Euro)

Tour Pompei ruins for 2-2.5 hours, not far from station (~20 Euro/pp)

Take Regionale, leave Pompei 2:11, arrive Napoli Centrale 2:52

Take taxi (~15 Euro) to Naples Archeological Museum (all the art from Pompei) (museo ~8 Euro)

Visit Museum 1-1.5 hrs, then leave museum, find nearby Napoli pizza (1 hr)

Take taxi back to Napoli Centrale (~15 Euro) Take train Napoli Centrale to Roma Termini either 6:40-7:48 or 7:00-8:10 (~35 E/pp)

I'd only try this in the off-season when the crowds aren't big. A little insane, yes, and a whirlwind nearly 12 hours, but you get to experience the transit system in southern Italy, plus you see the ruins and then the accompanying art, which is fabulous as a bookend to seeing Pompei. And then you can have some great Napoli pizza!

Enjoy your planning!

Thank you all so much. You've given me a lot to think about!

Jay's plan is definitely possible, especially in February when it isn't hot. You may want to buy Rome-Naples-Rome tickets in advance for the discount. Then, if it's rainy, go to Herculaneum - Pompeii will be too hard to get around in rain, part are hard enough to walk in dry weather.

Note that Herculaneum is a fifteen minute downhill walk from the Circumvesuviana station. Pompeii is right there. Herc has no food inside except a vending machine, and you can't re-enter if you go out to eat. Pompeii has a large tourist cafe near the main forum square.

I always fail to see why Herculaneum is better because it's smaller! Why would the failure to excavate more of the city be an advantage? It does have its own special attractions, but I prefer Pompeii, which is almost impossible to see in a full day. As Rick points out, Pompeii must have had a Synagogue ... it just hasn't been found, or is underneath the modern city of Pompeii. So we don't have all of that city either.

Both are great, but if I had to choose I'd say Pompeii. I don't think you will have big problems with crowds in February, plus it's a big place. My wife and I visited both in April 2007 and neither felt crowded at all. Try to do both if you can though.