I am taking a cruise in the fall which will stop in Salerno.I would like to hit Naples and Herculaneum or Pompeii. I've read Hurculaneum is better choise than Pompeii so how do I accomplish Napels and Hurculaneum or should I just pick one thing to do.
Trains between Salerno and Naples take 35 minutes to 1 hour, depending on type of train and whether it makes stops. The Circumvesuviana train between Naples and Herculaneum takes 17 minutes, and another 19 minutes between there and Pompeii. With those travel times in mind but not knowing how long you have in port, here are a few ideas.
Take direct (non-stop) train to Naples. Continue on to Herculaneum, tour, then return to tour Naples. Take direct train back to Salerno.
A more ambitious plan would be to take a regional train to Pompei (the new city - 20 minutes), walk to the Pompeii Scavi Circumvesuviana station (allow at least 45 minutes, views of the ancient Roman city during 2nd half of walk), take the Circumvesuviana to Herculaneum, tour and then go on to tour Naples. Take direct train back to Salerno. That would be a very busy day with a fair amount of walking, but you'd get a taste of all three places.
If you're time in port is fairly short, then see either just Naples or just Pompeii (take cab or city bus from Pompei train station to Pompeii Scavi to save time).