Itinerary Help

I used to try to travel as far and fast as possible when traveling Europe. But I finally decided it's better to travel better--and slower. Rome is one of the great cities of the world, and the city and its suburbs are worthy of the full 5 days allotted. When we were last there (2014), we found just about as many great regional travel sights as within the center city.
It's just a shame that you don't have another week in your trip that would give you time to visit Florence and Tuscany.
We're returning April 24, 2016 to see what we missed on our last visit.

I think that Plan B is better, mainly because Siena is not a day trip from Rome, and neither is Florence. Given your preferences, I would recommend Night 1 in Florence, then late in the day on Night 2, go to Siena and spend the night. Night 3 Tuscany. Night 4 & 5 Rome. You'll see plenty of the countryside, don't delay Rome too much, it's fantastic.

Similar to Plan B, but travelling to Rome on Tuesday evening, reading to hit the ground running in Rome the next morning.

Day 1 - Sunday am - Train (2hr 51min) from Naples to Florence (2 nts)
Day 1 - Sunday pm - Florence - Duomo, Piazza della Signoria, Ponte Vecchio, Piazzale Michelangelo
Day 2 - Monday - Siena excursion
Day 3 - Tuesday am - Florence - Accademia, Uffizi
Day 3 - Tuesday pm - Train (1hr 31min) from Florence to Rome (3 nts)
Day 4 - Wednesday - Rome - Colosseum, Forum, Trevi Fountain, Spanish Steps, Pantheon, Piazza Navona
Day 5 - Thursday - Rome - St Peters and the Vatican

Plan b much better. For your time constraints. Italy should not be rushed but savored. even train traivel takes half day or so , allow for it.

You are going to spend more time on a train traveling than seeing and experiencing Italy. For 5 days, I'd only pick one place. Maybe Florence and do day trips to Siena and San Gimignano - we used WalkAbout Florence for their BEST OF TUSCANY tour and their CHIANIT WINE & FOOD SAFARI and it was so wonderful. We just returned from 3wks in Italy and we spent 6 days in Florence. You don't want to miss the David, Duomo, San Croce Church and Leather School, Central Market, maybe the Uffizi, a walk across the Arno Bridge. You want to take it in & savor it, not rush thru it.

Or Rome for the Vatican, Colosseum, Forum, Pantheon, and a day trip to Pompeii.

If not, then your plan #2 is better. Traveling and moving takes 1/2 day at least.

https://www.walkaboutflorence.com/italy-tuscany-florence-tours?gclid=CL638rHT_8gCFVMvgQodTycJrA

remember to book you train tickets at 120 days out for the best deals. The RS Italy book is wonderful.

Less than 4.5 hours total on the train Naples - Florence - Rome is nothing over 5 days. Go for it.

I agree with the other posters...5 days is not enough to properly see more than 2 cities. Siena/Tuscan countryside would not be on my list if you've never seen Florence or Rome before. The big cities will give you more "wow" moments in a closer area...more bang for your buck. Stick to the big highlights with such a short timeframe.

For me, even at age 28, travel days between cities are almost always a bust...its very easy to underestimate how exhausting it is (and how much time it will take) getting from one place to another, checking in/out etc.

This is what I would suggest:
Sunday - 1/2 day in Florence (pick 1-2 sights to see in logical order, perhaps following Rick's suggested walk through the city)
Monday - Florence (pick 2-3 more sights to see in logical order)
Tuesday - Afternoon train to Rome (pick 1 sight to see. Note that everything is much busier/crowded after 10am)
Wednesday - Vatican
Thursday - Rome (pick 2-3 sights to see)