Koh Lanta or Koh Phi Phi?

Both islands have beautiful beaches, but they offer different things. Koh Lanta has length and choice: a chain of west coast bays that runs from the shallow, easy water of Klong Dao and the long casuarina-lined Phra Ae down to quiet coves near the national park, all facing the sunset and easy to reach by road.

Koh Phi Phi has the more spectacular setting, with turquoise water under limestone cliffs. However, its best swimming at Long Beach and Laem Tong is reached by longtail or footpath, because Loh Dalum turns shallow at low tide and fills up with day-trippers.

Koh Lanta eats better, mostly because it has its own food culture. Most islanders are Muslim, so southern Thai curries, roti and halal cooking are everyday food, there are night markets around Saladan, and the Old Town's stilt restaurants serve crab over the water.

Phi Phi's food is mostly Tonsai village menus of fried rice, pizza and burgers for backpackers, with ingredients brought in by boat. Banana roti from the carts and grilled seafood on the beach are the highlights. Neither island is a reason to travel for food.

Neither island is a culture trip, but Lanta at least gives you a half day of looking around. You can walk the wooden Chinese shophouses of the Old Town, a former trading stop between Penang and Phuket, and visit the Urak Lawoi sea-people village at Sang Ka U. Phi Phi has little more than a small tsunami memorial and the cliff mouth of Viking Cave, seen from a passing boat.

Phi Phi is clearly the party island. Every night the bars on Loh Dalum lay out mats, run fire dancing and serve drinks in buckets until the early hours, and reggae bars fill the village lanes. It is loud and young, and it is the same kind of night wherever you go.

Lanta's evenings are cushions on the sand along Long Beach and Klong Dao, a reggae soundtrack and a fire show, with an occasional party night in high season. Lanta visitors who want a big night take the boat to Phi Phi.

Phi Phi packs more drama into a small area. Sheer limestone walls rise from the sea, the climb to the viewpoint looks over both bays, kayaks slip into Pileh Lagoon, and blacktip reef sharks cruise the shallows at Shark Point. The reefs show wear from heavy boat traffic, and you can see most of the island in a few days.

Lanta is larger and gentler on land, with jungle trails and monkeys in Mu Ko Lanta National Park, caves in the forested interior and mangroves to kayak along the east coast. Its boats reach the Emerald Cave on Koh Mook and the deep pinnacles where mantas and whale sharks pass.

Each island is a classic day trip from the other, and both mostly offer boat tours to bays and islets, so neither is a strong base for outings. Lanta comes out a little ahead because its car ferry links it to the mainland by road, so Krabi Town and Ao Nang are reachable even when the boats stop. The fishing village on Koh Mook makes a gentle extra stop.

From Phi Phi, Railay and Ao Nang are about an hour and a half by boat, and Phuket Town's Sino-Portuguese shophouses make a long day there and back.

Lanta is the more natural family island. The northern beaches, Klong Dao especially, have soft sand and shallow water, family bungalows with pools are easy to find, and there is no party crowd. Neither island has zoos, aquariums or theme parks, though, and older children may get bored on either.

Phi Phi can work if you stay at Laem Tong, where the water is calm and children can snorkel with fish, and the lack of cars helps. The village is noisy late at night, the paths to the outer beaches are steep and unlit, and medical care is more basic than Lanta's community hospital.

On Phi Phi you walk. There are no cars, Tonsai and Loh Dalum are a few minutes apart through narrow lanes, and longtail boats reach the other beaches. It is also quicker to reach, with a direct ferry from Phuket, Krabi or Ao Nang.

Lanta has one road down the west coast and no buses. You get around by sidecar taxi, hired scooter or car, and little is walkable beyond your own beach. Arriving from Krabi airport takes two to three hours by road and car ferry.

Neither island is a place to shop, so bring what you need. What little there is differs in kind. Lanta has batik and craft shops in the Old Town's wooden houses and small night markets around Saladan. Phi Phi's village lanes sell practical things: snorkel and dive gear, sunscreen, tailoring and souvenir T-shirts.

Lanta is the easier island on a budget. Simple bungalows and guesthouses are plentiful, local food and massages cost little, and the quieter south and east coast are cheaper again. The main costs that add up are taxis and transfers.

On Phi Phi, everything arrives by boat and space is tight, so rooms in the dry season, drinks and longtail rides all cost more. Visitors also pay an entry fee for the island and the marine park. Backpackers in dormitories still manage, but the gap from normal Thai prices is obvious.

Neither island has a performing arts scene, and both offer fire shows on the beach and the odd acoustic band in a bar. The one real difference is Muay Thai. On Lanta it means bouts at small local rings, while on Phi Phi the fights are amateur ones staged inside bars for visitors as part of a night out.

Lanta is the better island for switching off, because the whole place is quiet. Yoga studios and retreats cluster around Long Beach and the southern bays, open-air massage pavilions line almost every beach, and Kantiang Bay is about as calm as a stay gets.

On Phi Phi, how restful your stay is depends on where you sleep. The resorts at Laem Tong and the isolated eastern bays have spas among the trees and slow hammock days, but anywhere near Tonsai the music carries late and day-trippers crowd the lanes.