Biarritz or Saint-Tropez?

Both are beach towns at heart, but the sea is very different. Biarritz faces the open Atlantic. The Grande Plage, the Côte des Basques and the long sands of Anglet are wide and handsome, but the waves are often big and the water stays fresh. Swimming means staying between the lifeguard flags, and Port Vieux is the one calm exception.

Saint-Tropez gives the easier swim. Pampelonne has about 5km of fine sand, and its clear water is a couple of degrees warmer at the height of summer. The southern coves such as Escalet and Cap Taillat are quieter, though the best beaches are out of town, not on its doorstep.

Biarritz is the better place to eat. Basque cooking gives it a real identity, and Les Halles is at the centre of it, with pintxos and local wine at the market counters, Bayonne ham, mountain sheep's cheese and fish from the Bay of Biscay, followed by gâteau basque and chocolate.

Saint-Tropez cooks Provençal food with polish, from bouillabaisse and aïoli to rosé lunches on the sand, and its top tables are genuinely good. The gap is in the middle. Honest, good-value meals are harder to find, many quayside places charge for the view, and much of the town shuts in winter.

Neither town is a culture destination, and both are seen quickly. Biarritz's heritage is its seaside resort architecture from the Second Empire to the Art Deco years: the former imperial villa, the Art Deco casino, the villas on the headlands, the Russian Orthodox church and the Rocher de la Vierge. The aquarium and the Cité de l'Océan add some museum time.

Saint-Tropez has less to see overall, but it has the finer single collection. The Musée de l'Annonciade holds pointillist and Fauvist paintings from the years when Signac and his circle painted the port, and the citadel and the ochre lanes of La Ponche complete the visit.

Saint-Tropez has the bigger and more famous summer night out. Afternoon parties at the Pampelonne beach clubs lead to champagne on harbour terraces and yachts, then to clubs that stay open until dawn, all with table service and a dress code. Biarritz is more relaxed and more modest. Its nights centre on wine and pintxos around Les Halles and surfers' sundowners above the Côte des Basques, with only a few clubs and the casino.

Both go quiet once the season ends. Biarritz makes up for it with Bayonne's old quarter and San Sebastián's bar streets close by, which give more variety than Saint-Tropez's single glamorous style.

Both are excellent outdoors, but on different terms. Biarritz is a surf town first, with beginner breaks and surf schools on the seafront. The green Pyrenean foothills start within half an hour, for walking up La Rhune or cycling around Sare and Ainhoa.

Saint-Tropez is about the Mediterranean shore: the coastal path out to the capes of Camarat and Taillat, sailing on the gulf, snorkelling off rocky points and the national park islands of Port-Cros and Porquerolles. Summer heat and fire risk push its walking into spring and autumn, while Biarritz's mild, rainy climate keeps its hills green.

Biarritz has the far richer choice, in two countries. San Sebastián is under an hour away, Bayonne's cathedral and riverside houses are next door and Saint-Jean-de-Luz is a short train ride down the coast. Inland are Espelette, Ainhoa and walled Saint-Jean-Pied-de-Port, and Bilbao's Guggenheim makes a long day by car.

Saint-Tropez's outings are pleasant but smaller in scale: hilltop Ramatuelle and Gassin, Grimaud's ruined castle, the canals of Port Grimaud by passenger boat, wine tastings on the estates and a full day on Porquerolles. None has the historic weight of the places across the Basque border.

Biarritz is the more practical family base. The seals and sharks at the aquarium and the Cité de l'Océan fill a wet afternoon, surf schools take children, and the sheltered Port Vieux cove suits the youngest. The steep streets are hard work with a pushchair, though.

Saint-Tropez has gently shelving sand for small children at Pampelonne and Gigaro, but little else is aimed at them. The cost, the hot afternoons and the adult tone of the harbour and beach clubs make long stays hard, and many families stay across the gulf in Sainte-Maxime instead.

Biarritz is much easier to get around. The centre, beaches and market are all walkable, if hilly. Buses run to Anglet and Bayonne, the airport is on the edge of town and coastal trains reach Saint-Jean-de-Luz and the Spanish border. A car is only really needed for the villages and the mountains.

Saint-Tropez itself is a few minutes from end to end, but it has no railway, the main beaches are several kilometres out and the single road along the gulf clogs for hours in July and August. The passenger boats from Sainte-Maxime and Port Grimaud are the most pleasant way in.

Saint-Tropez is the place to shop. The lanes behind the port hold a cluster of big fashion houses that few towns its size can match, along with resort wear, jewellery and the hand-stitched Tropézienne sandal. The Place des Lices market adds linen, baskets and pottery.

Biarritz is smart but small-scale, with boutiques and surf shops between the Place Clemenceau and the market. Its souvenirs are Basque: striped linen, espadrilles, chocolate and Espelette pepper. In winter Saint-Tropez loses much of its advantage, because many of its shops close.

Neither is cheap, but Saint-Tropez is in a different bracket. Biarritz charges resort prices too, especially in July and August, but pintxos at the market counters keep meals reasonable, and staying in Anglet or Bayonne cuts costs further.

In Saint-Tropez, rooms, loungers, harbour meals and even a coffee on the port are priced for the yachting crowd, and taxis or parking add to the bill. Budget visitors there usually sleep inland or across the gulf and come in for the day.

Biarritz has the livelier stage of the two, thanks to dance. A national choreographic centre with its own ballet company performs at the Gare du Midi, and an autumn dance festival fills the town's stages, though music and theatre beyond that are modest. Saint-Tropez has open-air concerts in summer and the centuries-old Bravade procession each May, and almost nothing to attend for the rest of the year.

Biarritz is built for this. It has been a sea-bathing town since the nineteenth century, and its large seafront spas offer heated seawater pools, algae wraps and multi-day cures that people plan a whole vacation around. Headland walks and watching the surf fill the rest of a slow off-season day.

Saint-Tropez relies on the spas of its luxury hotels, which are polished but meant for their guests. Its calm comes from the season, not the spas: in May, June and September the town slows to pétanque under the plane trees and morning walks up to the citadel.