In October my DH and I are taking a cruise along the southern coast of Italy. One day we have the choice of taking a shore excursion to either Pompeii or Herculaneum. While both are UNESO World Heritage Sites they appear to be somewhat different. From the little I have read I have gathered that while Pompeii is more well known, Herculaneum is better preserved due to it being covered in hot mud rather than hot ashes that burned everything during the eruption of Mt. Vesuvius. Any suggestions are appreciated.

Herculaneum is tiny - a large hole in the ground and as you say well preserved but Pompeii is much more vast and to me interesting - Pompeii IMO for sure.

Not everyone loves Pompeii - especially in the often torrid heat with little shade but it is Pompeii and if you do not see it you will always wonder what if...

I have seen both. I preferred Herculaneum. I would not visit Pompeii in summer - it is a very big site with no shade. Since Herculaneum is more intact you get a better feel for how it might have looked.

OCTOBER! for the reading impaired......I have not been to Herculaneum but have visited Pompeii twice - very worth the time.

October would be a fine time for Pompeii - far less crowds and probably just fine weather. can get guides at entrance if you want.

Trip along the southern coast.... which port would you be starting from, just to get an idea of the transfer time?

We will dock at Sorrento. Supposedly, the shore excursions both take 4.5 hours. I have no idea how much of that is travel time or visiting time. We're not adverse to skipping the shore excursion and traveling on our own if it would be cheaper.

Ah, Sorrento is just south of Pompeii (45 mins?) so up the west coast.