Leonardo ExpressorTAM bus?

The short answer

For one traveler the TAM bus is cheaper by €7. That does not change up to 8 travelers.

The Leonardo Express is quicker: 32 min against 50 min. The TAM bus varies between 30 and 65 minutes.

Leonardo Express: 05:38–23:27. TAM bus: 01:30–00:15.

Priced against each other

Whole-party totals · adult fares

What each costs for the whole party, in EUR. The cheaper of the two is marked on every row.
Travelers	Leonardo Express	TAM bus	Difference
1	€14	€7	€7
2	€28	€14	€14
3	€40	€21	€19
4	€40	€28	€12
5	€54	€35	€19
6	€68	€42	€26
7	€80	€49	€31
8	€80	€56	€24

Where each one leaves you

Leonardo Express · TrenitaliaLeonardo Express

Non-stop to Termini only. If you are staying in Trastevere or near Ostiense, the regional FL1 leaves you closer for less.

TAM · TAMTAM bus

From: Fiumicino Bus Station, Terminal 3 arrivals level — stand 17
To: Roma Termini, Via Giolitti 34
Luggage: One bag per passenger up to 15 kg is included, stowed in the hold; larger or extra bags need their own ticket.
Runs: 01:30–00:15
Journey: 30–65 min

The EUR 7 fare is the Basic ticket, valid only for the booked departure; buying from staff at the stop instead of online costs EUR 9.

Journey time varies with traffic: the timetable allows as little as 30 minutes late at night and up to about 65 minutes in the day.