Formentera or Mallorca?

Both islands have the same clear, warm water and the same swimming season, but on Formentera the beaches are the whole point. Ses Illetes is a thin spit of white sand with turquoise shallows on both sides, wilder Llevant lies just across it, and Migjorn runs for kilometres of sand and dune. The island is small enough that you can pick each day's beach by the wind.

Mallorca has more coast and more variety. There are the southeastern calas such as Caló des Moro and Cala Mondragó, the undeveloped dunes of Es Trenc, the long shallow bays of Alcúdia and Pollença, and pebble coves under the Tramuntana. Its prettiest coves are small, though, and fill early in summer.

On Formentera, food means a long lunch over the water: grilled fish, rice dishes and lobster stew at the chiringuitos, with island specialities such as peix sec in ensalada payesa and flaó for dessert. Away from those beach tables the choice thins out quickly, and many kitchens close when the season ends.

Mallorca has a fuller kitchen built on pork, olive oil and vegetables, from sobrassada and tumbet to an ensaïmada at breakfast. It also has the market life and wine that Formentera lacks: tapas bars in Santa Catalina, the Mercat de l'Olivar, vaulted cellers in Inca and Sineu, and local wine from Binissalem.

Formentera's heritage takes one day to see, fitted around the beaches: the fortified church in Sant Francesc, the lighthouses at Cap de Barbaria and La Mola, and the Bronze Age tomb of Ca na Costa.

Mallorca offers enough for a proper sightseeing trip. In Palma, La Seu stands over the sea wall beside the Almudaina palace, and there are also the round Bellver Castle, Es Baluard and the Miró foundation. Beyond the city are Chopin's charterhouse in Valldemossa, Alcúdia's walls, and talaiotic villages that are far larger than Formentera's single megalithic tomb.

A night out on Formentera means sunset drinks on the west coast and a few late bars on the Es Pujols seafront. Anyone wanting clubs has to take the ferry to Ibiza and plan the trip back.

Mallorca has every kind of night out. Palma has wine and cocktail bars in the old town and clubs on the Paseo Marítimo that run until dawn in summer, and Magaluf and Playa de Palma are large party resorts. The north coast and the mountain villages stay as quiet as Formentera after dinner, so the choice of base decides the evenings.

Formentera's landscape is low and bright, with salt pans, dunes and juniper scrub. Its best outdoor moments are gentle ones: flamingos on the Estany Pudent, snorkelling over the seagrass, and sunset walks on the La Mola cliffs.

Mallorca has real mountains. The Tramuntana rises to about 1,400m, the GR221 links its villages, and the Torrent de Pareis gorge and the Formentor cliffs make serious day walks. Cycling shows the difference best: easy green routes on Formentera, and the climbing hairpins to Sa Calobra on Mallorca.

Formentera has two outings. Ibiza is about half an hour away by fast ferry, for Dalt Vila and the villages of the north, and the uninhabited islet of Espalmador makes a half day.

Mallorca has a week's worth of outings without leaving the island. You can take the wooden train to Sóller, visit Deià and Fornalutx, spend market days in Sineu and Santanyí, and walk the walled town of Alcúdia. Boats run to the Cabrera archipelago, and a ferry from Alcúdia reaches Menorca for a long day in Ciutadella.

Formentera works for families who want nothing but the beach. The sheltered water at Ses Illetes is calm and shallow, and older children love the flat cycle routes. Beyond that there is nothing made for children, there is little shade on the sand, and the ferry adds a step after the flight.

Mallorca is built for family vacations. The bays of Alcúdia and Pollença and the beach at Cala Millor shelve gently, and the resorts around them have pools, kids' clubs and flat promenades. For days off the beach there are water parks, an aquarium near Palma and the boat ride across the underground lake in the Caves of Drach.

Getting to Formentera means a ferry from Ibiza into La Savina, but once you are there the island is only about 20km end to end. A bicycle or scooter covers it on quiet, flat roads, and one bus line links the villages.

Mallorca is easier to reach, with flights straight to Palma, and regional buses and a few rail lines connect the main towns and resorts. That covers a single-resort stay. To explore the coves and mountain villages, though, you will want a car, and in summer that means narrow, slow roads and car parks that fill early.

Shopping on Formentera is a pleasant evening's browse: linen and sandals in the boutiques of Sant Francesc, handmade leather and silver at the El Pilar de La Mola market, and crafts on the Es Pujols seafront.

Mallorca offers real shopping. Palma has fashion on the Passeig des Born and independent shops and delicatessens in the old town. The island's own crafts are leather and shoes from Inca, pearls from Manacor and striped roba de llengües cloth, and the weekly markets in Sineu and Santanyí sell ceramics and baskets.

Both islands cost more than mainland Spain in summer, but Formentera has no cheap way in. Rooms are scarce, beach lunches are priced for the resort, and the ferry and hire vehicle add to the bill.

Mallorca has the cheap options Formentera lacks. Package resorts in the north bays and on the east coast, set lunch menus and the village cellers keep costs down, though the boutique hotels near the coves are just as expensive. On both islands, May, June and late September ease the bill without giving up warm water.

Live performance on Formentera comes down to musicians at the La Mola market, sunset sets at a few beach bars and the odd small festival. The island has no theatre or concert hall.

Mallorca has a modest but genuine programme, and Palma holds most of it, with opera and theatre at the Teatre Principal and the Balearic Symphony Orchestra through the winter. In summer, as well as concerts in the courtyard of Bellver Castle, the music spreads across the island: classical festivals in Valldemossa and in Pollença's cloister, and ball de bot at village fiestas.

The two islands are about equal for rest, but they offer it in different ways. On Formentera the calm comes with the island: it is low-rise, with no big resorts, and days end in early nights, with yoga and massage easy to find in summer but only small spas.

On Mallorca you have to choose your calm. There are good spas in upmarket hotels, the Font Santa thermal spring near Es Trenc, country estates among olive and almond groves, and retreats in spring and autumn. All of this sits well away from the resort strips, which are anything but restful in midsummer.