US Virgin Islands or Puerto Rico?

The sea is warm all year at both, but the Virgin Islands have the edge for a pure beach trip. On St John's north shore, Trunk, Cinnamon, Maho and Hawksnest have calm turquoise water inside a national park with reef just offshore. On St Thomas, Magens Bay and Coki Point add sheltered swimming and snorkelling straight from the sand.

Puerto Rico has more coast and more variety. There are city beaches at Condado and Isla Verde in San Juan, the calm, palm-backed bay at Luquillo and the white horseshoe of Flamenco on Culebra. Much of its north coast faces open Atlantic surf, though, so swimmers need to choose their stretch more carefully than on St John.

Puerto Rico is by far the better place to eat. Mofongo, arroz con gandules and whole roast pig at the Guavate lechoneras make up a cuisine worth travelling for. San Juan adds the creative kitchens of Santurce, the market square at La Placita and coffee from the mountains.

The Virgin Islands have honest West Indian cooking, such as kallaloo, fungi, johnnycakes and pates, and it is at its best on St Croix. Most ingredients are imported, though, and visitor menus on St Thomas and St John lean American. You eat well enough there, while in Puerto Rico the food can shape the whole trip.

Old San Juan gives Puerto Rico a real cultural centre: a walled Spanish colonial town whose forts, El Morro and San Cristóbal, are part of a UNESCO site. Beyond it are the art museums in Santurce and Ponce and the Taíno ball courts at Caguana and Tibes.

The Virgin Islands' heritage is Danish rather than Spanish. It is best seen in the arcades of Christiansted and Fort Christiansvaern, the synagogue in Charlotte Amalie with its sand floor, and the Annaberg and Whim plantations. It is worth seeing, but it fills a few half-days rather than the slow day or two that Old San Juan alone deserves.

San Juan gives Puerto Rico a proper night out. On weekends crowds drink in the street at La Placita, the salsa and reggaeton bars on Calle San Sebastián start late and run into the small hours, and the Condado adds casinos and clubs.

Nights in the Virgin Islands mean open-air rum bars in Red Hook, Cruz Bay and along the Christiansted boardwalk, full of charter sailors, and most nights end early. The late nights come only with carnival on St Thomas and the Crucian Christmas festival.

Puerto Rico has the wider range of landscape. It has the El Yunque rainforest under an hour from San Juan, the karst hills and Río Camuy caves, the coffee country of the Cordillera Central, three bioluminescent bays and serious winter surf at Rincón.

The Virgin Islands are smaller in scale but strong on the water. St John's park trails, such as Reef Bay, and the underwater snorkelling trail at Buck Island are lovely, and the sheltered sailing water is some of the easiest in the Caribbean. Keen hikers will run out of trails within a few days.

Neither is a great base for days out, but Puerto Rico has more variety. You can visit Ponce's plaza and art museum, the rum distilleries at Cataño, the coffee haciendas and the old church town of San Germán, while Culebra and Vieques are better with a night or two.

From St Thomas the outings are almost all islands and beaches: St John by short ferry, tiny Water Island, and the British Virgin Islands if you have a passport. The days out start to feel alike.

Both suit families who are happy on beaches and in the water, and neither has much built for children. Puerto Rico has more to do on land, with waterfall trails in El Yunque, the guided route through the Camuy caves and kite-flying on the lawns of the old forts. It also means more driving and keeping away from the rough north-coast beaches.

The Virgin Islands are smaller, and their bays are calmer for children. Young snorkellers can swim near turtles at Maho Bay, and Coki Point has touch pools, though steep roads and hilly resort grounds tire small legs.

Both are hard to explore without a car or taxi, but the problems differ. Puerto Rico is a road trip on good highways, with heavy traffic around San Juan, slow mountain roads and ferries to Culebra and Vieques that often sell out or run late.

The Virgin Islands have short distances but steep, narrow roads where traffic keeps left. Shared safari taxis run on St Thomas and St John, and the Red Hook ferry links those two easily, while St Croix needs a flight or a long ferry ride.

Neither is a shopping destination, so the difference is in what you buy. Puerto Rico has crafts with a story: carved santos, vejigante masks from Loíza and Ponce, guayabera shirts, mountain coffee and aged rum, plus large American malls in Hato Rey. In the Virgin Islands the draw is duty-free watches and jewellery in the old warehouses along Main Street in Charlotte Amalie, with island-made pieces such as the St Croix hook bracelet in Cruz Bay and Christiansted.

Puerto Rico costs roughly what the mainland US does, and the Virgin Islands cost more again. On Puerto Rico, food is where you save, at roadside lechoneras, beach kiosks and local fondas. Guesthouses in Rincón and on the west coast cost less than hotels in San Juan, although a hire car adds to the bill.

In the Virgin Islands the extra cost shows up everywhere: in resorts and villas on St John, in groceries shipped in from elsewhere and in shared taxis that charge per person. The best of the islands is free or close to it, since the beaches and park trails cost little, and St Croix and the campgrounds on St John are the cheaper places to stay.

Puerto Rico has both living street music and a formal stage. Bomba in Loíza and Piñones, plena around La Placita and salsa dance nights sit alongside the Centro de Bellas Artes, home to the symphony orchestra, as well as Teatro Tapia and the long-running Casals Festival.

The Virgin Islands have their own traditions in quelbe, steel pan and the mocko jumbie stilt dancers. You mostly hear and see them by catching a festival or a band at a beach bar, though, and there is no regular programme of concerts or theatre.

Neither has a real bathing culture, and both rely on resort spas for pampering. Puerto Rico adds the old hot springs at Coamo and the yoga and easy surf-town pace of Rincón, but San Juan itself is loud and full of traffic.

In the Virgin Islands, rest comes from the slow pace: hammocks, little traffic noise and early evenings on St John and the east end of St Croix. That quiet is closer at hand than Puerto Rico's own restful corners on Vieques and Culebra.