This is the question almost every traveller asks before booking their first night on Sri Lanka's south coast, and most answers online dodge it. They say "it depends on what you're looking for" and list a few vague pros and cons. Here's a more direct answer, based on the kind of travellers we talk to every day.
Weligama is the best base for most first-time visitors. The bay is calm, the surf is beginner-friendly, the food scene is excellent without being overpriced, and you can reach Galle, Mirissa, Ahangama and Hiriketiya all as day trips. It has the infrastructure of a popular town without the overcrowding. If you don't know where to stay and you're not a specific type of traveller, Weligama is the safe, correct answer.
Mirissa is for people who want a beach-first trip and don't mind a more touristy atmosphere. Whale watching is the draw, and the beach itself — especially the stretch toward Coconut Tree Hill — is genuinely beautiful. But Mirissa's main strip has become loud and repetitive. The restaurants on the beachfront are expensive and mediocre. The nightlife attracts a certain crowd. If you're coming for whale watching between November and April, stay one or two nights and move on. Don't base yourself here for a week expecting a peaceful trip.
Hiriketiya is for a very specific type of traveller: slow-paced, surf or yoga-oriented, and comfortable spending most of the day within a small bay. It's a horseshoe-shaped beach with a reliable left-hand wave, good cafes, no loud bars, and almost nothing to do in the evenings apart from eat well and sleep early. That is the point. If that sounds like a good trip to you, Hiriketiya is exceptional. If you want to explore, move around, and see different things each day, you'll feel trapped after three days.
A few practical points. Weligama has the most ATMs and the most transport options. Mirissa has essentially one road, which gets congested. Hiriketiya has no ATM so bring cash. All three are within 30 minutes of each other, so splitting time between them is easy and worth doing.
The comparison travellers almost never think to make is Ahangama versus all three. Ahangama sits between Galle and Weligama, is quieter than either, has a strong cafe and restaurant scene, good surf at Kabalana, and feels like the version of the south coast that existed five years ago. Worth considering if you've already done Weligama before.
If you're still not sure which town fits your trip, that's exactly the kind of question we answer when we put together a custom itinerary. Tell us how long you have, what you're after, and we'll give you a specific answer.