The taxi situation at Tunis-Carthage Airport is the defining factor in this comparison. Understanding it helps you decide which approach suits you.
The taxi experience
Yellow taxis are abundant outside the terminal during the day. All taxis have meters. The problem is that many drivers prefer not to use them for airport runs, quoting a fixed price that is two to four times the metered fare instead.
The metered fare to central Tunis is genuinely cheap: 8-15 TND ($3-5 USD) during the day. But if a driver quotes you 30-50 TND and you do not have the language skills or confidence to push back, you end up paying significantly more.
If you speak French, firmly say the destination and indicate the meter. Most drivers will comply, even if reluctantly. If you do not speak French, this interaction is harder to navigate, especially when tired.
Payment is cash only. Taxis do not accept cards.
The transfer experience
A pre-booked transfer removes the meter negotiation entirely. The price is set when you book, typically $15-30 USD to central Tunis. The driver waits with your name, the vehicle is known, and there is no discussion about price when you arrive.
This is more expensive than a metered taxi but often comparable to what a tourist-priced taxi would charge. The premium is for convenience and predictability.
When the taxi wins
If you speak French or Arabic, arrive during the day, carry cash in Dinars, and are comfortable insisting on the meter, a taxi is hard to beat. At $3-5 USD, it is one of the cheapest airport taxi rides in the world.
When the transfer wins
If you arrive at night (when the nighttime tariff and reduced taxi availability complicate things), do not speak the local languages, travel with family and luggage, or simply do not want to start your trip with a negotiation, a transfer is worth the extra cost. The difference between $5 and $25 is small in absolute terms, and the comfort of walking out of the airport and getting into a waiting car is significant when you are tired.
A note on ride-hailing
Ride-hailing apps have limited presence in Tunisia. Do not count on them as a reliable alternative. The practical choice is between a taxi from the rank and a pre-booked transfer.
The bottom line
The metered taxi from Tunis Airport is extremely cheap. The challenge is not the price but the interaction required to get that price. A pre-booked transfer pays a premium for skipping that interaction. Neither option is wrong; it depends on your comfort level and language ability.