Termini vs. Tiburtina Train Stations

Either station works and it is wise to wait til you arrive to purchase that ticket
Just purchase next journey once you have cleared passport control and have your baggage

There are multiple trains every hour
If you purchase in advance you risk missing your train and have to buy a new ticket

Both Trenitalia and ItaloTreno run fast trains
Get the easy to use apps and use only the official sites

You will take the Leonardo Express to Terminal ( 14 euros, every 15 min)

If you choose Tiburtina you take a regional train from FCO not sure how frequent

Termini is simple and would be my choice
It is not a complicated station to maneuver

https://www.trenitalia.com/en.html
https://www.italotreno.com/en

Station names
Roma Termini
Firenze SM Novella

How do you plan to travel from the airport (assuming FCO) to the train station? If you propose to travel by train, the Leonardo Express from FCO goes straight to Termini where you would then connect with a train to Florence (Firenze).

Pardon my presumptuousness, but I would go on to suggest that you download the Trenitalia (state operated train system) and Italo (privately operated Italian trains) apps and set up your accounts.

Once on the Leonardo Express from the airport to Termini, buy a ticket for the next available train (with a comfortable connection) from Termini to Florence (Firenze). While I would otherwise purchase high speed train tickets in advance, when air travel is involved, I purchase corresponding train tickets on the fly. There are just too many things that can go awry and mess up your time table.

Buonviaggi

Well, I think you'll need to commit to one or the other and be prepared to deal with any
issues resulting from delays getting through FCO to downtown Rome (deplaning, EES/
immigration, baggage delays, getting lost going to/at the train station, etc).

Look at the schedules for each station adding ~2+ hours to your arrival time to see
how often trains run from each to Florence.

I have not transited through Tiburtina, but I would concur that if travel times are ~equal
(there's a good chance they are) and you have backup options if you miss your original
train, then Tiburtina is perhaps a better option.

You will save a few shekels taking a regional train to Tiburtina, but nothing to get excited about.

Something completely different.

I don't know when you will land, but if it works timewise I would plan on buying some food in the station (Termini or Tiburtina) and eat on the train. We have done this often in Italy and other countries. This way you get better food cheaper. Build in some time to shop, when you buy the ticket.

My preference would be Termini. Even though it is large, it is not difficult to navigate. Do be prepared for the possibility of a long wait time when landing in Rome. We flew into FCO last month, and it took 2 hours to get through the EES System. You have been given good advice to purchase a train ticket once you are at Termini. The Trenitalia app is very user friendly.

Thanks for all the advice. It was recommended to purchase the high-speed train to Florence before as it is quite expensive to purchase when you arrive. I was planning on leaving close to four hours from the time I land to when the train leaves Rome. However, from all your advise, I may just purchase at the time. Saves the stress of missing something already booked.

Everyone has to do what suits them best, but…I am glad you decided (for this ticket) to purchase as you go. For day of arrival train tickets I apply the equation higher cost = less stress.

Our dear friends last fall (3 couples) were adamant about purchasing their tickets from Termini to Bologna ahead of time and their flight was delayed leaving Atlanta. They then missed their train from Termini to Bologna which they had already paid for, and then had to buy new tickets.