Puerto Rico or Saint-Martin?

The beaches are equally good, but the two islands deliver them differently. Puerto Rico's coast is spread out: city beaches such as Condado and Isla Verde a walk from San Juan hotels, the calm palm-lined bay at Luquillo, and the finest sand offshore at Flamenco on Culebra. Its north coast faces the Atlantic, so winter surf and currents rule out swimming on long stretches.

Saint-Martin packs its beaches into a small area. Orient Bay is the lively one with sunbeds and water sports, while Baie Rouge, Baie Longue and Happy Bay on the leeward side are quiet and clear enough to snorkel from the shore. The catch here is drifting seaweed on the east-facing bays in some months, rather than heavy surf.

The two eat about equally well, in different ways. Puerto Rico has more breadth: roast pig carved at the roadside lechoneras of Guavate, fritters at Piñones, and in San Juan the creative kitchens of Santurce around La Placita and the classic dining rooms of the old town, plus rum and mountain coffee.

Saint-Martin's strength is concentrated in Grand Case, where French and creole dining rooms over the water sit beside the lolos, open-air barbecue stalls with shared tables. Good bakeries and French cheese and wine add a European touch, though a week exhausts the options.

Here Puerto Rico is far ahead. Old San Juan is five centuries of Spanish colonial town on a walled islet, with the great forts of El Morro and San Cristóbal, and beyond the capital there are Ponce's plaza and art museum, San Germán's old church and the Taíno ball courts at Caguana and Tibes.

Saint-Martin offers the ruins of Fort Louis above Marigot, a few streets of creole houses and a small museum. It is a morning's sightseeing on a beach trip, not a reason to go.

Puerto Rico has the real night out. On weekends La Placita de Santurce fills with people drinking in the street, Calle San Sebastián in Old San Juan is packed with bars, and dancing to salsa and reggaeton starts late. Condado and Isla Verde add casinos and polished hotel lounges.

On the French side of Saint-Martin, evenings mostly mean a long dinner and a drink at Grand Case or a sunset beach bar at Orient Bay. For clubs and casinos past midnight you cross the open border to Simpson Bay and Maho on the Dutch side.

Puerto Rico offers far more landscape. El Yunque's rainforest of tree ferns and waterfalls is under an hour from San Juan, the bioluminescent bays on Vieques, near Fajardo and at La Parguera glow at night, and the karst country hides the Río Camuy caves. Winter brings big surf and passing humpback whales off Rincón.

Saint-Martin is greener than expected, with forest trails up Pic Paradis at about 424m and a treetop park, but most of its outdoor life is on the water: turtles and rays in the reserve around Tintamarre, and steady trade winds for kitesurfing at Orient Bay.

Neither island is a great base for outings, and the trips are of different kinds. From San Juan they are mostly drives: Ponce on the south coast, the rum distilleries across the bay and the coffee haciendas in the mountains. Culebra and Vieques are the best of them, though they are better with a night or two than as a rushed day.

From Saint-Martin, a day trip almost always means another island. Anguilla's quiet beaches are a short ferry ride from Marigot, St Barths has the chic harbour at Gustavia, and Saba and Sint Eustatius make a long day out. Rough seas can make the crossings uncomfortable.

Puerto Rico gives families more to fill the days. Beyond calm water at Luquillo and Seven Seas, there are short trails to waterfalls and pools in El Yunque, a guided route through the Camuy caves, resort kids' clubs around Río Grande and Dorado, and lawns at the old forts for kite flying.

Saint-Martin's appeal for families is mainly its shallow sea, at the reef-sheltered bay of Le Galion and on Pinel, along with villas with kitchens and pools. Beyond a zipline park and watching planes at Maho there is little else for children, and neither island has a theme park.

On both islands you will want a hire car, but the scale is very different. Puerto Rico is a road trip, with Rincón about two and a half hours from the capital, heavy traffic round San Juan and slow mountain roads. Old San Juan is walkable, and the ferries to Culebra and Vieques often sell out or run late.

On Saint-Martin nothing is more than about forty minutes away, and the border to the Dutch side is open and unmarked. Narrow roads and jams at the lagoon bridges are the irritations, and water taxis handle Pinel and Tintamarre.

Neither is a shopping destination, though Puerto Rico has a little more to offer. The streets around Calle Fortaleza in Old San Juan sell carved santos, vejigante masks, cigars and aged rum, and the big malls in Hato Rey cover everyday needs.

Saint-Martin splits between Marigot's waterfront market and French boutiques and the duty-free jewellery and electronics shops along Philipsburg's Front Street. Guavaberry liqueur is the most characterful souvenir.

Neither is cheap, but Puerto Rico is the easier on the budget. Prices are at American levels and San Juan's beachfront hotels are dear in winter, but lechoneras, beach kiosks and fondas keep food costs down, and guesthouses in Rincón and the west cost less than hotels in the capital.

Saint-Martin charges high Caribbean rates for rooms and French prices or more for meals, with car hire and boat trips on top. The lolos and supermarket picnics help, and travelling in late spring or summer brings rates down.

Puerto Rico has a living music culture of its own. Bomba drumming in Loíza and Piñones, plena around La Placita and salsa dance nights are easy to find, and the January Fiestas de la Calle San Sebastián fill the old town. For formal evenings there are the Puerto Rico Symphony at the Centro de Bellas Artes, plays at Teatro Tapia and the Casals Festival.

Saint-Martin has no theatre or concert hall. Music means steel pan, zouk or soca at beach bars and hotels, with Carnival the one real high point of the year.

Puerto Rico has a little more for a restful trip. Its big resorts at Dorado and Fajardo have full spas, Vieques and Culebra slow almost to a standstill, Rincón has yoga, and the hot springs at Coamo offer a modest bathing tradition dating from colonial times. San Juan itself is noisy, though.

Saint-Martin has no spa tradition, only resort spas and a few yoga spots. What it offers is a slow pace: a villa above Anse Marcel or a quiet cove on the west coast, away from Marigot's traffic.