Koh Phangan or Phu Quoc?

These are two equally strong beach islands with different kinds of beach. Koh Phangan has small bays of varied character: the twin bays of Thong Nai Pan, Bottle Beach reached by longtail boat, and the easy swimming at Haad Yao and Haad Salad. Its long southern shore is reef flat, too shallow to swim at low tide.

Phu Quoc has length instead. Long Beach runs about 20km down the west coast, lined with resorts and facing the sunset, and the whitest sand is at Sao and Khem in the southeast. The seasons differ too. Koh Phangan's east coast gets rough from October to December, while Phu Quoc's west coast is at its worst from May to October.

Phu Quoc has the better and more distinctive food. Seafood is picked live from tanks along the coast, the island has its own dishes such as raw herring salad wrapped in rice paper, and you can visit the fish sauce houses and pepper farms behind two products known across Vietnam. The stilted restaurants over the water at Ham Ninh make an evening of it.

Koh Phangan eats well but more plainly: curries and som tam from family kitchens, grazing at Thong Sala's night market and Saturday walking street, and Srithanu's vegan cafés for a change. Neither island has much in the way of fine dining.

Neither island is a place for sightseeing, and an afternoon covers the sights on either. Phu Quoc has a little more to stop for, above all the prison museum near An Thoi from the French and American wars, along with the Dinh Cau shrine and the Ho Quoc Pagoda on its hillside. Koh Phangan's heritage is quieter and more spiritual: old temples such as Wat Phu Khao Noi and Wat Khao Tham, and the royal initials carved into the rocks at Than Sadet.

This is where the two differ most. Koh Phangan is a party island known around the world. Every month the Full Moon Party fills Sunrise Beach at Haad Rin until after dawn, half-moon and jungle parties are held inland, and the west coast has its own gentler sunset bars and ecstatic-dance nights.

Evenings on Phu Quoc are much quieter. You get sundowners on Long Beach, a few bars in Duong Dong, and crowds walking the lit-up resort districts or visiting the casino in the north. Most people are back at their hotel well before midnight, and outside the dry season it is quieter still.

The two are fairly close outdoors, with Koh Phangan slightly ahead. Its steep, forested interior has trails to Khao Ra, about 630m high, and waterfalls such as Phaeng. Offshore, Sail Rock is one of the Gulf's best dive sites, and boat days go out to the limestone lagoons of Ang Thong.

Phu Quoc is flatter and mostly about the water. It has national park forest in the north, pleasant reefs around the An Thoi islands, and the long cable car to Hon Thom, which gives the best view over the archipelago.

Koh Phangan has the better days out, mainly because Koh Samui is only about half an hour away by boat, with the Big Buddha and the old Chinese shophouses of Fisherman's Village. Koh Tao is close enough for a day of snorkelling around Koh Nang Yuan. Phu Quoc offers little beyond island-hopping boats to the An Thoi archipelago and the ferry to Ha Tien, a quiet border town with a temple hill. On both islands, most visitors spend their days at their own beach.

Phu Quoc is clearly the easier island with children. The north has an open-range safari park and a theme park with rides and an aquarium, and the Hon Thom cable car ends at a water park. Big resorts with pools and kids' clubs line the shore, which is shallow and calm in the dry season.

Koh Phangan works if you choose your part of the island with care. The gently shelving bays at Thong Nai Pan, Haad Yao and Haad Salad are good for small children, but there is nothing built for them. Avoid Haad Rin, especially around the full moon.

Phu Quoc is the easier island to get around, even though it is bigger. Electric buses run along the main spine from the airport through Long Beach and Duong Dong to the northern resort district, and ride-hailing and metered taxis cover the rest. Even so, most outings mean half an hour or more on the road.

Koh Phangan has no real public transport, only shared songthaews and app taxis, so most visitors rent a scooter on steep and sometimes gravel hill roads. Distances are short, but Bottle Beach is still easiest to reach by longtail boat.

Neither island is a shopping destination, so the difference lies in what you bring home. Koh Phangan's shops sell for the beach and the yoga mat: loose cotton clothes and cheap jewellery from the Saturday walking street in Thong Sala, neon party wear in Haad Rin, and yoga clothing and crystals in Srithanu. There are no malls or design boutiques, and anything more serious waits for Bangkok.

Phu Quoc's best buys are what the island produces: black pepper, cultured pearls from its farms and dried seafood from the Duong Dong evening market, though airlines may not allow the fish sauce in your luggage. The resort districts have rows of shops, but nothing in fashion, design or craft is worth a special trip.

Both islands are good value by international standards, and there is little between them. On Koh Phangan, a long stay in a simple bungalow on the west coast is the cheapest way to live, but rooms in Haad Rin around the full moon cost several times the usual rate.

On Phu Quoc, guesthouses near Duong Dong, market seafood and taxis cost little. The money goes on the theme parks, the cable car, boat trips and the big resorts, especially in the dry-season peak around the turn of the year.

Neither island has a theatre, a concert hall or any real tradition of live performance, so the difference is the kind of evening entertainment. Phu Quoc stages large shows for tourists in its resort districts, with water, fireworks, lights and drones by the sea. Koh Phangan's music is small and informal: acoustic and jam nights around Srithanu, music at the ecstatic-dance gatherings and fire-dancers on the sand at Haad Rin.

Koh Phangan is far ahead here. Srithanu and the coast around it are among Asia's best-known places for yoga, meditation, silent retreats, breathwork and detox programmes, and people come for a week's course or stay for months. Wat Khao Tham has long run Buddhist meditation retreats.

Phu Quoc's version of rest is simpler: cheap Vietnamese massage, herbal baths in resort spas, some yoga, and the quiet north coast around Ong Lang and Ganh Dau. It is restful, but nothing on the island compares with Srithanu's retreats.