Koh Phangan or Koh Samui?

Both islands are built around beach life, and the difference lies in the kind of beach. Koh Phangan's best bays are tucked away. Thong Nai Pan and Bottle Beach in the north have soft sand and deep, calm water, but you reach them by winding roads or by longtail boat, and the long southern shore turns to shallow reef flats at low tide.

Koh Samui's beaches are long, open and built up. Chaweng is a broad sweep of white sand with everything behind it, Lamai is a little rougher, and Choeng Mon is the sheltered one for slow swimming. On Samui you get convenience and company on the sand, while on Phangan you get more seclusion.

Koh Samui eats better, mostly because there is more of it. Night markets run in Lamai, Maenam and along Bophut's Fisherman's Village, and there is a tier of polished restaurants with sea views in the hillside resorts and on the Bophut waterfront.

Koh Phangan's food is good everyday Thai cooking, centred on the evening market and Saturday walking street in Thong Sala. Srithanu adds a cluster of vegan and raw cafés for the yoga crowd. Fine dining barely exists, so for a special dinner Samui is the island to be on.

Neither island is a place to visit for heritage, but Koh Samui has a bit more to see on a half-day loop. There is the gilded Big Buddha on its causeway islet, the many-armed Guanyin at Wat Plai Laem, the mummified monk at Wat Khunaram and the old Chinese shophouses of Bophut.

Koh Phangan's sights are quieter and more local: the old temple of Wat Phu Khao Noi, the meditation temple of Wat Khao Tham, and the royal initials carved into the rocks at Than Sadet. If you are staying on Phangan, you can see Samui's main sights in a day across the water.

Koh Phangan is the island people travel to for the party. The Full Moon Party fills Sunrise Beach at Haad Rin with tens of thousands of people, and half-moon and jungle parties fill the nights in between. The west coast offers a gentler alternative in sunset bars and sober ecstatic-dance gatherings.

Koh Samui's nightlife is more conventional resort-town fare. Chaweng has beach clubs, bars along the main road and a cluster of clubs, and Lamai has a smaller, rougher scene. Much of it is generic, and Samui visitors who want the big night cross to Haad Rin for it.

Koh Samui has a slight edge, mainly because Ang Thong National Marine Park is its signature outing. Boat trips take you kayaking and snorkelling among the limestone islands, and there is an emerald saltwater lake inside one of them. On land there are the Na Muang waterfalls and jeep tracks through the coconut plantations.

Koh Phangan's interior is steeper and wilder. Trails climb to Khao Ra at about 630m and pass the Phaeng and Than Sadet waterfalls. The island also lies closer to Sail Rock for divers, and boats from Phangan reach Ang Thong too.

From either island, a day trip means taking a boat to a neighbouring island, and the two are about level. From Koh Phangan, Samui is the obvious change of scene, with the Big Buddha, Bophut's shophouses and bigger shops. Koh Tao is only about an hour away for snorkelling at Koh Nang Yuan.

From Koh Samui, the outing works the other way round. Phangan offers quieter beaches and a looser backpacker feel, and Koh Tao is a longer trip that fills the whole day. Neither island has historic towns within reach, and the mainland ports are only transport hubs.

Koh Samui is clearly the better island for children. Many resorts on Choeng Mon, Bophut and Maenam are designed for families, with large pools and children's clubs. Beyond the beach there are small animal parks, a water park, elephant sanctuaries and boat trips to Ang Thong for older children.

Koh Phangan can work in the calm, gently shelving bays of Thong Nai Pan, Haad Yao and Haad Salad, and the sandbar walk to Koh Ma is a simple pleasure. But nothing on the island is built for children, the roads are steep, and Haad Rin around the full moon is no place for a family.

Koh Samui is easier to get around. A single ring road of about 51km links every beach, Chaweng to Bophut takes around a quarter of an hour, and hire cars and ride-hailing cars are easy to find. The island also has its own airport, which saves a ferry leg.

On Koh Phangan, most visitors rent a scooter on steep, sometimes gravel roads or rely on songthaews waiting at the pier. Some of the best bays are hard to reach: Bottle Beach is easiest by longtail boat, and the eastern coves sit at the end of winding roads. Scooter accidents are common on both islands, so take care if you ride.

Koh Samui has the wider range. The Friday walking street in Fisherman's Village is a pleasant evening browse for crafts and coconut-wood homeware. Chaweng has a large modern mall with international chains, and the tailors there make suits to measure.

Koh Phangan's shopping is casual and narrow. You will find loose cotton clothes at the Thong Sala Saturday walking street, neon party wear in Haad Rin, and yoga clothing and crystals in Srithanu. Neither island is worth visiting for its shopping, but on Phangan anything beyond the basics means a trip to Samui.

Koh Phangan is the cheaper island, and it is particularly good value for long stays. A beach bungalow, meals from local kitchens and scooter hire on the west coast cost very little. The big exception is Haad Rin around the full moon, when rooms are booked out and cost several times the usual rate.

Koh Samui is one of the dearest places to stay in Thailand. Its resorts and hillside villas are priced for international visitors, taxis are expensive and flights to the island add to the bill. It can still be kept modest if you stay back from the beach, eat at night markets and base yourself away from Chaweng.

Neither island has a theatre or concert hall, and serious performance means going to the mainland. The difference is in the kind of show. Koh Phangan's live music is informal and homemade: acoustic sets, reggae jam nights and the music at the ecstatic-dance gatherings around Srithanu, with fire-dancers on the sand at Haad Rin.

Koh Samui offers entertainment aimed at visitors. There are Muay Thai fight nights at small stadiums around Chaweng and Lamai, ladyboy cabaret shows and cover bands in the bars.

Both islands are among Asia's established places to slow down, but they offer different kinds of retreat. Koh Phangan's wellness scene is a community. It is centred on Srithanu, with yoga shalas, silent retreats, breathwork and sound healing, and many people come for a course and stay for months. Wat Khao Tham adds Buddhist meditation retreats.

Koh Samui leans towards programmes and comfort. Lamai and the hills behind it are known for detox and fasting stays, and there are lavish hillside resort spas looking over the Gulf. On either island, the quiet north and west are the places to stay, well away from the party areas.