San Pedro de Atacama or Valparaiso?

San Pedro is a desert oasis at 2,400m, a long way from the Pacific, so there is no beach to speak of. The nearest thing to a swim is an hour floating in the salt-heavy water of Laguna Cejar or the Baltinache pools, under a fierce sun with no shade, and then rinsing off the salt.

Valparaíso wins easily, even though its own waterfront is docks and rocks. The coastal train takes you to the sandy beaches of Viña del Mar, and further up the coast beyond Viña are the wide beaches of Reñaca and Concón. The cold Humboldt water and strong waves mean most people sunbathe and walk along the shore, with only a quick dip.

Valparaíso eats a good deal better. Its cooking comes from the sea and the port: fish fresh from coves like Caleta Portales, conger eel soup, machas and late-night chorrillanas. Up on the cerros there are more ambitious kitchens pouring Casablanca whites.

In San Pedro, eating out means one dusty main street of restaurants serving tour groups. The best of them use Andean ingredients such as quinoa, llama and rica-rica, but there are no markets or street food, and the menus start to feel repetitive within a few days.

Valparaíso is a sight in its own right. You can spend days on its UNESCO-listed hills of merchant houses and funiculars, at Neruda's house La Sebastiana and among the murals and the old prison turned cultural park.

San Pedro's heritage takes about half a day. It comes down to the cactus-wood ceiling of its adobe church, the Pukará de Quitor fortress above the river and the ancient round dwellings at Tulor. All of it is worth cycling to, but it is a backdrop to the desert rather than a reason to come.

The two are far apart here. Valparaíso's nights begin in wine bars on Cerro Concepción and end in clubs around Subida Ecuador, where the students stay out until morning. It is rough around the edges, so taxis between neighbourhoods are a good idea late at night.

San Pedro offers a pisco sour by a fire pit and an early night before the pre-dawn geyser run. Your night out there is an astronomy tour rather than a bar.

San Pedro is one of the most remarkable landscapes in South America. It has eroded valleys for sandboarding, flamingos on the Salar de Atacama, El Tatio steaming at sunrise and deep blue lagoons beneath volcanoes, though the altitude means you need a few days to acclimatise before going high.

Valparaíso's outdoors is gentler and at sea level. There are cliff walks towards Quintay, the Concón dunes, surf at Ritoque, penguins off Cachagua and Darwin's summit in La Campana. It is pleasant, but it is not why most people visit.

Valparaíso has the more varied list. Viña del Mar is right next door, Santiago is a full day out, and the Casablanca wineries, Neruda's house at Isla Negra and the villas of Zapallar are all within easy reach.

From San Pedro, nearly every excursion is into the landscape rather than to another town. Toconao's white-stone village, the old church at Chiu Chiu and the vast copper mine at Chuquicamata are the main alternatives, and Uyuni is too far for a day trip.

Teenagers are the ones who get the most out of San Pedro, with sandboarding on the dunes, floating in a salt lagoon and looking at Saturn through a telescope. With toddlers it is hard going, because of the pre-dawn starts, long minibus drives and outings above 4,000m in bitter morning cold.

Valparaíso is the easier choice for younger children. They can ride the funiculars, take a boat trip round the harbour and spend time on Viña's beaches and at its summer fun fair. The stairs and broken pavements are hard work with a pushchair, which is why many families stay in Viña and visit the city for the day.

In Valparaíso you can manage without a car. Colectivos, buses, trolleybuses, the funiculars and the coastal train cover the city, even if the hills make every walk a climb. In San Pedro the village is ten minutes across on foot, but there is no public transport to anything worth seeing, so the landscape means a tour, a hired high-clearance car or a hard bike ride.

San Pedro's shopping is a craft market by the plaza and the stalls along Caracoles. They mostly sell the same alpaca and wool goods you find across the region, though a warm jumper is genuinely useful for the freezing dawns. Valparaíso gives you more to browse, with galleries and craft studios on Cerro Alegre and a weekend flea market full of old maps, vinyl and nautical oddities. For malls and fashion, you would still go on to Viña or Santiago.

Valparaíso is noticeably kinder to a budget. Guesthouses in the lower town, cheap set lunches at picadas, transport that costs very little and free wandering through the murals and viewpoints keep daily spending modest, as long as you stay off the polished hilltops.

San Pedro costs more than most of Chile, because supplies are trucked across the desert and almost every sight needs a paid tour or park entry. Cycling and set lunches help, but only a little.

Valparaíso has a real music culture of its own. Cueca porteña and old boleros play in traditional bars, there are bands in small venues and concerts at the Teatro Municipal, although opera means a trip to Santiago. In San Pedro you might hear the odd panpipe player in a restaurant, and the festival dances for San Pedro and San Pablo and for Carnival are the only real performances.

For rest and restoration, San Pedro comes out ahead. The Puritama hot pools step down a reed-filled canyon, the desert lodges have spas facing the volcanoes, and the slow pace of adobe courtyards suits doing nothing, provided you leave a few days free of early tours.

Valparaíso has no bathing tradition and only a handful of hotel massage rooms. Its quiet moments are a terrace coffee above the bay or a cliff-top promenade at dusk.