My fi and I took a Mediterranean cruise on the Norwegian Jewel (left from Barcelona and went to Italy & France). We didn’t think twice about booking our excursions through Norwegian. Yes, they are pricey, but they were worth every penny.
Not sure if yours is the same itinerary as ours, but since most of them are similliar, here is some info on our trip:
The ports are very far from the actual cities. We went to Rome, and the closest port was Civitavecchia–it was close to a 2 hour ride. We went to Florence, and the port was Livorno, which was like 1.5 hours to Florence. For these two cities a tour is a must do, first of all because the ports are just ports–nothing to do around them. If you tour on your own, you will get stuck paying ridiculous amounts of money on a cab ride because you would not chance a bus or public transportation when you are on a tight schedule (I heard horror stories on the costs of cab rides from other guests).
Naples is a port itself, so if you want to save money on that day its easy that day you can just spend the day walking around and eating yummy Pizza. We took an early trip to Pompeii, which was 2 hours if not more, and then came back in time to grab some pizza in Naples before we had to get back on the ship.
We also went to Messina, and took a 1.5 hour trip to Taormina. The port of Messina has nothing to do, it’s industrial. So the trip to Taormina was worth it, we spent that tour doing some sightseeing and then the rest of that day was on a beach called ‘Naxos’ (black volcanic sand, very cool).
We went to Villefranche-Sur-Mer and there is no need to spend money on a tour because you can walk right up to the very inexpensive train and arrive in Nice, Cannes, Montercarlo in a matter of minutes. Or you can just stay in the quaint town of Villefrance (charming cafes, calm beach etc).
Keep in mind that the best about booking your tour through the shipping line is the comfort of an air conditioned bus or van and then knowing that if you get stuck in traffic etc. the ship won’t leave until you get there. If you are on your own the ship doesn’t wait!
I suggest you do research on the ports of call and find out how far they are from the actual cities and then decide if you think its worth paying the cost of a tour/excursion.
If you are going to any of these destinations and want more info on which tours we took, you can PM me.