Martinique or Saint-Martin?

Both islands have excellent beaches, but they feel different. Martinique's best are separate coves on the Caribbean side and the southern tip. There is the palm-lined curve of Grande Anse des Salines, turtles grazing close to shore at Les Anses-d'Arlet, and the black-and-gold pair of Anse Noire and Anse Dufour.

Saint-Martin's beaches sit closer together and are more varied in mood. Orient Bay is a long, sociable strip with sunbeds and water sports. Baie Rouge and Baie Longue are quieter, and Pinel is a small islet a short boat ride away. Its eastern bays can collect seaweed in some months, whereas Martinique's Atlantic side is simply too rough for most swimming.

Martinique's eating is spread across its rum country, while Saint-Martin's is concentrated in one seafront village. On Martinique, the cane estates of the north and centre pour rhum agricole for tasting, and a ti-punch comes before most meals. Some of the best colombo, blaff and grilled conch comes from roadside stalls and beach shacks, and the covered market in Fort-de-France sells spices and hot sauces.

On Saint-Martin, Grand Case does most of the work. French and creole dining rooms over the water stand beside the lolos, where ribs and grilled lobster are served at shared tables. That makes it easy to eat well night after night, though a week covers most of it, and the rest of the island adds little beyond beach restaurants and bakeries.

Martinique has much the deeper heritage. Saint-Pierre, destroyed by Mount Pelée in 1902, is a powerful visit to ruins beneath the volcano. Fort-de-France adds the Schoelcher Library and its cast-iron cathedral, and the island also has Empress Joséphine's birthplace and the Anse Cafard slavery memorial.

Saint-Martin offers the view from Fort Louis over Marigot, a few streets of painted creole houses and a small museum. That fills a morning, not a theme for the trip.

A night out on Martinique means driving to the zouk and kompa clubs around Fort-de-France, which fill late at weekends with a mostly local crowd. Otherwise, evenings end early after a ti-punch at a beach bar in Sainte-Anne or Les Trois-Îlets. Carnival is the exception, with parades and drumming late into the night until King Vaval burns on Ash Wednesday.

On Saint-Martin, the late options are a short drive across the open border, where the casinos and clubs of Simpson Bay and Maho stay open well past midnight. On the French side, Grand Case has street music and late terraces on busy winter nights, and the beach bars at Orient Bay draw a crowd at sunset.

Here Martinique is in another league. Its UNESCO-listed volcanic north includes Mount Pelée at around 1,400m, the rainforest of the Pitons du Carbet and gorges you can descend by canyoning. Offshore, there is diving at Diamond Rock and on the Saint-Pierre wrecks, and you may see whales in season.

Saint-Martin's highest point, Pic Paradis, is only about 424m, with forest trails and a zipline park. Its real outdoor strength is the water: the Tintamarre reserve for snorkelling with turtles and rays, and Orient Bay's steady trade winds for kitesurfing.

Saint-Martin has the edge because it sits among other islands. Anguilla's quiet beaches are a short ferry ride from Marigot, and St Barths' chic Gustavia makes a contrasting day out. Saba and Sint Eustatius are within reach for a longer outing, and Philipsburg is just across the border.

Martinique's best outings are on the island itself: a tour of the rum estates around Sainte-Marie and Le Robert, the fishing villages of the far north, and the sandbanks off Le François. Dominica and St Lucia are reachable by fast ferry, but each takes a long day.

Both work for families because of calm, shallow bays rather than attractions built for children. Martinique's Anse Mitan and Grande Anse d'Arlet let children snorkel with turtles right off the sand, and French healthcare makes the practical side easy. The drawback is distance: winding roads and traffic make outings tiring.

Saint-Martin is small enough that the reef-sheltered bay at Le Galion or the boat ride to Pinel never involves a long journey. Older children usually enjoy watching the planes come in low at Maho.

You need a hire car on both islands, and buses on either will not get a visitor to the beaches reliably. What differs is scale. Martinique is big enough that the drive north on steep roads, and the rush-hour jams around Fort-de-France and Le Lamentin, take real time. The ferries across the bay to Les Trois-Îlets are a pleasant way to skip some of it.

On Saint-Martin, nothing is much more than about forty minutes away, the open border with the Dutch side costs no time, and water taxis handle the hops to Pinel and Tintamarre. The congestion is concentrated around Marigot and the lagoon bridges.

Saint-Martin is the better place for shopping, largely because of its Dutch half. Philipsburg's Front Street is a long run of duty-free jewellery, watch and electronics shops, and Marigot adds French boutiques, perfume and a waterfront market.

Martinique's shopping is about what the island makes. The best buys are aged agricole rum from the estates, vanilla and hot sauces from the Fort-de-France market, madras cotton and craft-village pottery. Otherwise it has little beyond mainland chain stores.

Neither is cheap, but Martinique costs less to stay on. A self-catering gîte, fish and fruit bought at roadside stalls, and free or inexpensive rum tastings keep a stay within reach, even with French prices and an island premium.

Saint-Martin charges high Caribbean rates for rooms in the popular bays, restaurants match or exceed French prices, and boat trips to the islets and neighbouring islands add up. The lolos and supermarket picnics help, and rates ease outside the winter season.

Martinique has a real living tradition to seek out. Bèlè drum-and-dance evenings in the villages of the north and centre welcome visitors into the circle. Fort-de-France has a national arts centre with year-round theatre and dance, plus a long-running July festival, though formal shows are in French.

Saint-Martin has no stage or concert hall at all. Steel pan, soca and reggae come with dinner at Grand Case or a beach bar, and Carnival's calypso contests are the one time music becomes the main event.

Neither island has a spa or bathing tradition, so relaxing comes down to pace and a good base. Martinique adds a few warm volcanic springs in the northern forest to its resort spas at Les Trois-Îlets and Sainte-Anne, and its south slows naturally to swims and long lunches.

On Saint-Martin, the quietest retreats are a villa above Anse Marcel or a west-coast cove. They are best kept well away from the cruise-day crowds around Marigot.