Rome and Naples sit less than an hour apart by train, but they represent two very different Italy's — the grand, monument-heavy capital versus the chaotic, unpolished birthplace of pizza and gateway to Pompeii.
Rome's Colosseum, Roman Forum, and Pantheon are astonishingly well preserved and sit right in the modern city center. Naples' own Royal Palace of Naples is grand but overshadowed by what's nearby — Pompeii, a short train ride away, is a more complete ancient site than anything in Rome itself.
Rome's Vatican Museums & Sistine Chapel is one of the greatest art collections on earth. Naples counters with the National Archaeological Museum, which holds the best surviving artifacts from Pompeii and Herculaneum, and the eerily lifelike Sansevero Chapel veiled Christ sculpture.
Naples is where pizza was invented, and it shows — a Neapolitan margherita here is a different, better thing than what's served almost anywhere else, at a fraction of Rome's prices. Rome's food (pasta alla carbonara, cacio e pepe) is excellent too, but it's priced for a capital city and a constant stream of tourists.
Rome is polished, well-signed, and set up for tourists, with excellent transport and a much larger hotel selection. Naples is grittier and more chaotic, with a reputation for petty crime that puts some travelers off — but it rewards those who visit with cheaper prices and a rawer, more authentic Italian city.
Choose Rome for the concentration of world-famous sights, the Vatican, and an easier, more tourist-friendly trip. Choose Naples for cheaper, better pizza, easy access to Pompeii and the Amalfi Coast, and a grittier slice of real Italian life. They're under an hour apart by high-speed train, so combining both is easy and common.