Colonia del Sacramento or Valparaiso?

Neither city is a beach destination, and the difference is in kind. Colonia's sandy river beaches start at the edge of the old town, and the Río de la Plata is warm enough for a long wade in midsummer. But the water is brown and still, and algae can make swimming unwise in hot spells.

Valparaíso's sand is a train ride away in Viña del Mar, Reñaca and Concón. These are proper ocean beaches with waves and clear water, but the Humboldt Current keeps the sea so cold that most people only take a quick dip. For warm, calm paddling choose Colonia; for surf and open sea choose the Chilean coast.

Valparaíso has the more interesting food. It has dishes of its own: fish straight from the coves at Caleta Portales, conger eel soup, machas and the shared chorrillana of the port bars. The restaurants on Cerros Alegre and Concepción add more ambitious Chilean cooking with Casablanca Valley whites.

Colonia's range is narrower: grills, chivitos and pasta served in courtyards under the plane trees, many of them aimed at day-trippers. Its strength is the Tannat from the vineyards around Carmelo, and dinner by the river at sunset is a pleasure even if the food is not the reason to come.

Both have a UNESCO-listed historic quarter, but Valparaíso gives you more to explore. Its hills of painted corrugated-iron houses, the 19th-century funiculars, the merchant banks of the old port, Neruda's La Sebastiana and the Open Air Museum murals fill two or three days of wandering.

Colonia's Barrio Histórico is smaller and more unified. Its Portuguese and Spanish colonial lanes, the Calle de los Suspiros, the lighthouse over the convent ruins and a cluster of small museums are easy to see in a single day.

This is where the two differ most. An evening in Colonia means dinner, wine and the sunset, perhaps a last drink in a small pub, and the town is asleep long before late. Anyone who wants a real night out takes the ferry to Buenos Aires.

Valparaíso has a student-driven scene. It moves from cocktail bars on the hills down to the port bars and the clubs around Subida Ecuador, where people stay out until dawn at weekends, and Viña del Mar adds clubs and a casino. It is rough around the edges, so taking taxis between areas late at night is sensible.

Valparaíso sits on a far more varied coast. There are cliff walks towards Laguna Verde and Quintay, the Concón dunes, surf at Ritoque, sea lions in the bay and Humboldt penguins off Cachagua. Darwin's summit hike in La Campana National Park adds a mountain day, so an active traveller can stay busy for several days.

Colonia's landscape is flat river shore and cattle pasture. The riverside rambla is lovely for a sunset cycle and calm days allow some kayaking, but there are no hills or wildlife sites to head for.

Colonia has the most striking single outing: Buenos Aires, about an hour away by fast ferry, with one joint passport check per crossing. Beyond that the trips are gentle ones: the family wineries of Carmelo, Swiss-founded Nueva Helvecia and the British-built core of Conchillas.

Valparaíso's list is longer and more varied. Viña del Mar is on the doorstep, Santiago makes a full day by bus and the Casablanca wineries are under an hour inland. Along the coast there are Neruda's house at Isla Negra, the old whaling cove of Quintay and the villas of Zapallar, enough for several days without repeating yourself.

Colonia is the easier place with children. It is small, calm and safe, and riding golf carts or bikes along the river, paddling in shallow summer water and climbing the lighthouse keep most children happy, though the cobbles are hard work with a pushchair.

Valparaíso has its treats in the funiculars, the harbour boat trips and the murals. But the constant stairs, broken pavements, traffic and street dogs wear families out, which is why many stay in Viña del Mar, with its beaches and summer fun fair, and visit for the day.

Getting around Colonia is much simpler. The old town is tiny, the ferry and bus terminals are a few minutes' walk away, and a bike or golf cart on the flat riverside road reaches the beaches and Real de San Carlos. The only real nuisances are the rough cobbles and wineries too far out to reach without a car.

In Valparaíso every neighbourhood sits up a hill, so you rely on funiculars that do not always run, buses and shared colectivos. The trolleybuses in the flat lower town and the coastal train to Viña del Mar are useful and you need no car, but expect a lot of climbing.

Neither city is a shopping destination, and both are about crafts rather than fashion. Valparaíso has a little more to browse: galleries and studios on Cerros Alegre and Concepción selling prints, ceramics and lapis lazuli, and a weekend antiques market near Plaza O'Higgins for old maps and nautical oddments. Colonia's craft shops and seasonal stalls are best for leather, wool and a mate gourd with a silver bombilla.

Valparaíso is the cheaper base. Guesthouses in the lower town and quieter hills, set lunches at the picadas and almost free buses, colectivos and funiculars keep daily spending low. The stairways, murals and viewpoints cost nothing, and only the polished hilltops charge international prices.

Colonia's old town prices itself for visitors, with hotels and restaurants costing about what a Southern European resort would, and weekends push room rates up further. Staying a few streets out and drinking the local wine helps.

Valparaíso has a living music culture that Colonia lacks. Cueca porteña, boleros and old waltzes in the traditional bars and street musicians on the cerros give you something to hear on most nights. The Teatro Municipal and the arts centre in the old prison add formal performances, and Viña del Mar's song festival each February is a national event.

Colonia has occasional concerts in its restored riverside bastion and the odd guitarist or tango set over dinner in summer. For proper theatre or a tango show, you take the ferry to Buenos Aires.

Colonia is the place to unwind. Once the day-trippers leave the old town goes quiet, and slow lunches, siestas and riverside rides set the pace. A few hotel spas and countryside winery stays add pools and treatments, though there is no bathing tradition.

Valparaíso is noisy, steep and gritty, and its spa offer is a few massage rooms, with larger hotel spas over in Viña del Mar. Rest there means a slow morning on a terrace above the bay or a cliff-top promenade watching the ships.