At an airport this small, the question is less about taxi versus transfer and more about whether you want someone waiting or are happy to wait a few minutes.
Bolt or local taxi
Bolt is the dominant ride-hailing app in Estonia — it was founded here. Open the app at EPU, request a ride, and a driver arrives in 5-15 minutes. Fare: 5-8 EUR to central Pärnu.
Alternatively, call a local taxi company. The fare will be 8-12 EUR including pickup. Either way, you get a metered or app-calculated ride with a licensed driver in a standard vehicle.
Advantages: Cheapest option. Flexible — no advance commitment. Bolt is transparent on pricing.
Disadvantages: No taxi waits at EPU by default. You must order one after landing and wait. On rare occasions (events, bad weather), wait times could be longer. No child seat guarantee.
Pre-booked transfer
A driver is at the terminal when you walk out. Vehicle and price are confirmed in advance.
Advantages: Zero wait time. Driver tracks your flight. Child seat available on request. Good for onward journeys (Tallinn, Tartu, Saaremaa).
Disadvantages: More expensive (15-25 EUR for what is essentially a 5-minute ride). Requires planning ahead.
When each makes sense
Bolt/taxi works if: You arrive during normal hours, have the app installed, your phone has charge, and you do not mind a brief wait.
Transfer works if: You arrive at an unusual time, are continuing beyond Pärnu, travel with small children needing a car seat, or simply want someone there when you land.
The honest assessment
For most travellers, Bolt is perfectly adequate for EPU. The ride is so short that the difference in experience between a taxi and a transfer is minimal. The main reason to pre-book is either peace of mind or a practical need like a child seat or onward journey. If you are heading to Tallinn or another city straight from the airport, a pre-booked transfer makes clear sense — you do not want to coordinate a Bolt for a 130 km trip.