Bilbao or San Sebastian?

San Sebastián has the real beach city. La Concha curves round its sheltered bay a few steps from the old town, with calm water and a promenade made for summer evenings, Ondarreta is the quieter family stretch beyond it, and Zurriola across the river takes the open Atlantic swell for surfers.

Bilbao has no beach of its own, since it sits inland on the estuary. The metro reaches Ereaga and Arrigunaga in Getxo, the surf sands at Sopelana and the gentler bay at Plentzia and Gorliz in under an hour, which makes a good afternoon out but not a beach stay.

Both cities live by the pintxo crawl, txakoli poured at the counter and Basque produce cooked with restraint, so neither will disappoint. San Sebastián has the edge: the bars of the Parte Vieja and Gros are packed shoulder to shoulder, each with its own speciality, several of Spain's most celebrated restaurants sit in the hills around town, and from January to spring the cider houses of Astigarraga add a feast of their own.

Bilbao's version is just as serious if less famous, centred on Plaza Nueva, the Casco Viejo and the Ensanche, with the Ribera market on the river and asadores grilling txuleta steaks. In both, the limit is the same: international food is scarce.

Bilbao has the stronger sights. Gehry's Guggenheim is a destination in itself, the Museo de Bellas Artes holds old masters and Basque painters a short walk away, and the Vizcaya Bridge at Portugalete adds a UNESCO site by metro.

San Sebastián's appeal is the townscape rather than its collections: the belle époque streets, the rebuilt grid of the Parte Vieja, the castle on Monte Urgull and Chillida's Peine del Viento in the rocks at Ondarreta. The San Telmo Museum is its one major museum, and two or three days cover either city.

Bilbao keeps going for longer. Beyond the old-town pintxo bars there is a younger strip around Calle Licenciado Poza and more alternative bars near the Ribera, and weekend nights run well past 3am, though clubs are few.

In San Sebastián the evening is excellent until dinner ends, then the choice narrows to a handful of late bars in the old town and Gros and a few clubs along the bay. Each city has its August blowout, Aste Nagusia on Bilbao's riverbanks and Semana Grande with fireworks over La Concha.

Both sit among green hills and both are rainy, but the emphasis differs. Bilbao leans inland and towards the mountains: Gorbea's beech forests and the limestone peaks of Urkiola are within an hour, and down its coast lie the Urdaibai reserve, the stairway to San Juan de Gaztelugatxe and Mundaka's famous wave.

San Sebastián is the better place for coastal walking straight from town, with the path from Monte Ulia to Pasaia and the cliffs of Jaizkibel on to Hondarribia. Kayaking and paddleboarding in the sheltered bay are easy additions.

Both are excellent bases, and each makes the other's best day trip, a little over an hour apart by bus. What differs is the direction. Bilbao looks west and south, to Vitoria-Gasteiz, Cantabria's Santillana del Mar and the Altamira cave museum, and the fishing ports of the Bizkaia coast.

San Sebastián's trump card is France: Saint-Jean-de-Luz, Biarritz and Bayonne are within an hour, walled Hondarribia is half an hour away, and Pamplona is an easy run inland. Rioja wine country is reachable from either.

San Sebastián is the easier choice with children. Calm beaches sit in the centre beside a car-free promenade, and it has the attractions Bilbao lacks: an aquarium with a walk-through tunnel, the hands-on Eureka science museum and the old funfair at the top of Monte Igueldo.

Bilbao is safe, flat and welcoming, with Doña Casilda Park, the riverside promenade and the Artxanda funicular, and Puppy outside the Guggenheim delights small visitors. But with no zoo, aquarium or theme park, rainy days need more planning, and the beach is a metro ride away.

Both are easy without a car, in different ways. Bilbao strings its sights along a few kilometres of river, so the walk is longer, but the tram runs the same stretch and Foster's metro reaches the coast and the Vizcaya Bridge.

San Sebastián is smaller still: the old town, the centre, La Concha and Gros are minutes apart on foot, bike lanes run along the waterfront, and Euskotren trains go to the French border at Hendaye.

Bilbao offers a little more. The Gran Vía and the Ensanche have the main chains and a large department store, and the Casco Viejo keeps old family shops for berets, linen and cookware alongside independent design stores.

San Sebastián is smaller in range, with chains and neat boutiques in the Centro and surf shops in Gros, and big department stores are thin. In both, the best buys are edible: txakoli, Idiazabal cheese and tinned anchovies from the markets.

Neither is cheap for Spain, but Bilbao is clearly the gentler on the wallet. Its central hotels are mid-priced by Western European standards, and a pintxo crawl with a few glasses of wine is good value.

San Sebastián is among the most expensive cities in Spain to sleep in, because rooms are scarce and summer pushes them to big-capital levels. The walks and beaches are free, but travelling outside the peak is the main way to save.

Bilbao has the steadier programme through the year. The Euskalduna hosts the ABAO opera season and the Bilbao Symphony Orchestra, the Teatro Arriaga and Campos Elíseos stage theatre and dance, and BBK Live brings international bands in July.

San Sebastián is a festival town. Jazzaldia in July and the Quincena Musical in August fill the Kursaal and even Zurriola beach, but outside summer the Kursaal and the Teatro Victoria Eugenia offer a quieter season.

San Sebastián is the more restful stay. Its seaside resort past survives in the thalassotherapy spa in the old bathing pavilion on La Concha, with seawater pools facing the bay, and the calm promenade sets an unhurried pace.

Bilbao has only hotel and urban day spas. Its slow lunches and riverside walks are pleasant, but a real spa stay means a separate trip to the balnearios inland.