Marbella or San Sebastian?

Both have a fine town beach, but Marbella has far more beach. There are over two dozen of them along its shore, from La Venus and El Fuerte to the dunes at Cabopino, with chiringuitos, sun loungers and a season that runs from June into October. The sand is greyish rather than white, and a westerly wind can chill the water for a day or two.

San Sebastian's La Concha is the lovelier city beach: a sheltered shell of pale sand, with Ondarreta beside it and Zurriola for surfers. The Bay of Biscay holds it back, though. The season is short, and grey days interrupt even July and August.

This is where San Sebastian pulls furthest ahead. An evening moving between the pintxo counters of the Parte Vieja and Gros with a glass of txakoli is one of the great eating experiences in Spain. Behind it are the La Bretxa and San Martin markets, an exceptional group of celebrated restaurants in the hills and the winter cider houses of Astigarraga. Its one gap is variety, since nearly everything is Basque.

Marbella has that variety, from international dining to tasting menus on the Golden Mile, and sardines grilled over driftwood on the beach are a real pleasure. But the middle ground near the port is tired and overpriced, and good everyday meals take some finding in the old town and the streets inland.

San Sebastian has more to see, and the city around it hangs together better. There is the baroque Basilica of Santa Maria at the end of the Parte Vieja, the castle on Monte Urgull, the elegant 19th-century streets around Buen Pastor, the San Telmo Museum and Chillida's iron sculptures on the rocks. It rewards two or three days.

Marbella's heritage fits into an afternoon: the Plaza de los Naranjos and its whitewashed lanes, the print museum, the Dalí bronzes on the Avenida del Mar and the Roman villa at Río Verde. For anything more substantial you drive to Málaga or Ronda.

Marbella is the place for a big night out in summer. Beach clubs with DJs along the Golden Mile carry on into evening parties, and Puerto Banús keeps its champagne bars and clubs full until dawn. The style is polished and expensive rather than underground, and from November to March it goes quiet.

San Sebastian's evenings are sociable but end earlier. The pintxo bars of the Parte Vieja are loud and lively from early evening, but after that there are only a few late bars and clubs. The night usually ends where dinner does, except during August's Semana Grande.

Both put serious walking close to your hotel, but the landscapes could hardly be more different. Marbella backs onto the dry limestone of Sierra Blanca, with a hard half-day climb to La Concha peak and views to Morocco, and the fir forests of Sierra de las Nieves inland. Its mild winters make it a year-round walking base, though the coast itself is heavily built up.

San Sebastian is green and wet, with cliff paths from Monte Ulia to Pasaia and over Jaizkibel to Hondarribia, and surf at Zurriola. Pack waterproofs in any month.

The real split is between going by car and going by train or bus, and between one region and two countries. Marbella has no railway and its buses are slow, but with a hire car Andalusia opens up: Ronda above its gorge, Málaga, Gibraltar, the white villages of Casares and Mijas and, on a long day, Granada and the Alhambra.

San Sebastian's outings work without a car. Buses run to Bilbao and walled Hondarribia, the Euskotren goes to the French border, and from there Saint-Jean-de-Luz and Biarritz are close. The Rioja Alavesa vineyards are a further option, less than two hours away.

For families it is a choice between a beach-and-pool stay and a compact city with the sights close together. Marbella has sheltered, lifeguarded town beaches and resorts built around pools. An animal park, a zoo, water parks and a marine park are spread along the coast and are easiest to reach by car, and July and August are very hot.

San Sebastian keeps things within easy reach. The aquarium with its walk-through tunnel is at the harbour, and short bus rides take you to the Eureka science museum in Miramon and to the funicular up to the old funfair on Igueldo. Rain can rule out the beach for days, though, and after three or four days most families start planning excursions.

The gap here is wide. San Sebastian is small and flat. The Parte Vieja, La Concha, Gros and Zurriola are minutes apart on foot, bike lanes run along the waterfront, and the Euskotren goes to the French border and towards Bilbao.

Marbella stretches thinly from San Pedro to Cabopino along the motorway. The old town and the promenade are pleasant on foot, but getting to the port, the hotels and the villages means slow buses, taxis or a hire car.

If you shop for labels, Marbella is the better choice. In Puerto Banús, international fashion and jewellery boutiques face the yachts, with a department store and malls close by, and the old town adds leather, linen and ceramics. Beyond the big names, though, there is little independent design.

San Sebastian's shopping is smaller and more local: Spanish chains and independent boutiques in the Centro, espadrilles and berets in the Parte Vieja, and surf shops in Gros. The best souvenirs are edible, such as txakoli, Idiazabal cheese and tinned anchovies from the markets.

Neither is a cheap Spanish destination, and both raise room prices sharply in summer. In Marbella the expense is in beach clubs, sunbeds in the best spots and dinners around Puerto Banús. Tapas in the old town stay at ordinary Andalusian levels, and staying in a neighbouring town is a common way to save.

In San Sebastian the problem is a shortage of hotel rooms, especially in festival weeks, and its famous restaurants are a real splurge. A pintxo crawl, the free beaches and walks help, and in both cities avoiding the summer peak makes the biggest difference.

San Sebastian has much more live music and theatre. In July, Jazzaldia brings international names to the Kursaal and free concerts to Zurriola, and the Quincena Musical fills August with orchestral music and opera. The Kursaal and the ornate 1912 Teatro Victoria Eugenia have a programme through the rest of the year.

Marbella has little beyond a summer pop and rock festival in an old quarry amphitheatre, flamenco staged for visitors and a modest municipal theatre. For serious classical music or flamenco you have to go to Málaga.

Neither has a bathing culture you could plan a trip around, but they relax you in different ways. Marbella is a resort-spa destination, with wellness retreats, detox clinics and large hotel spas on the Golden Mile and in the hills, plus a few Arab-style baths. It is restful from October to May and much less so in the summer heat and crowds.

San Sebastian's main draw is the seawater thalassotherapy spa in the historic bathing pavilion on La Concha, a legacy of its days as a royal resort. Its calm, orderly pace and evening walks along the promenade do the rest.