The real difference is not the price, it is where you end up
ADO runs from the terminal to bus stations on a fixed timetable. If you are staying a few blocks from one, that is a short walk and a good deal. If you are staying on the Tulum beach road, in a gated development like Puerto Aventuras, or anywhere off the highway, the bus is the first of two journeys — and the second one you will be arranging with luggage, in a town you do not know yet.
That second leg is the part people forget when they compare the headline price. Count it before deciding, or the cheaper option stops being cheaper.
What a fixed timetable means after a delayed flight
A bus leaves when it leaves. If your flight lands late, you wait for the next departure — and at some hours that is a real wait. A private transfer works the other way round: we track your flight, so a delay moves your pickup instead of costing you a ticket, and the waiting time is included.
That matters most on exactly the arrivals where you are least able to improvise: the late ones.
When the bus is clearly the right answer
One or two travellers, light luggage, a daytime arrival, and a hotel near a bus station: take the bus. It is cheap, it is reliable and it is not a downgrade.
We would rather say that plainly than pretend a private transfer wins every comparison. It does not — it wins the ones with a group, an awkward destination, small children, or a flight that lands after midnight.
Where each one gets you
For Playa del Carmen and Tulum the bus is a real alternative, because both have a central bus station. For the Tulum hotel zone, Puerto Aventuras or Akumal, the bus leaves you some distance from where you are actually sleeping.