San Diego or San Francisco?

This is where the two cities differ most. San Diego's coast is made to be used: Coronado's broad, flat sand, the boardwalk crowd at Mission and Pacific Beach, gentle beginner surf at La Jolla Shores and calm, sheltered water at Mission Bay for small children. The water is cool early in summer but warm enough for a proper swim by August.

San Francisco's beaches are scenic rather than swimmable. Ocean Beach and Baker Beach are for walks, bonfires and views of the Golden Gate Bridge. The Pacific stays cold all year, and rip currents make Ocean Beach unsafe to enter. Anyone who wants to swim will end up in a hotel pool.

Both cities love a big burrito, but the depth is different. San Diego is at its best eating casually: Baja-style fish tacos, the California burrito stuffed with fries, late-night taco shops, a dense craft-beer scene and the Asian kitchens along Convoy Street.

San Francisco is the place for a trip built around meals. Dungeness crab, sourdough and cioppino give it real local dishes. Chinatown, North Beach and the Mission add range, and its fine dining and Napa and Sonoma wine lists go well beyond anything San Diego offers. Come to San Diego for the beer and to San Francisco for the cooking.

San Francisco has the more famous sights and the stronger museums. The Golden Gate Bridge, Alcatraz, the cable cars and the painted Victorians around Alamo Square are images people travel to see. SFMOMA, the de Young, the Legion of Honor and the Asian Art Museum give it serious art.

San Diego's culture is gathered in Balboa Park, where one day among the Spanish Colonial Revival buildings covers its main museums. Beyond the park are the USS Midway, the adobes of Old Town and California's first mission. It keeps more early colonial history than San Francisco, where the 1906 earthquake and fire destroyed much of the older city, but it has less to fill several days.

Neither city is one people travel to for nightlife, and both stop serving at 2am. Still, San Francisco gives more to a night out. The Mission's mezcal and cocktail bars, North Beach's old saloons, the Castro and the SoMa warehouse clubs offer more variety and a more inventive cocktail culture.

San Diego's nights are louder but confined to fewer places. There are rooftop bars and clubs in the Gaslamp, a rowdy student strip in Pacific Beach, and taprooms and cocktail bars in North Park and Hillcrest. It suits an easy evening over a beer better than a long night.

Both are excellent bases for the outdoors, but the landscapes are very different. San Diego's is warm and dry: surfing almost everywhere, sea lions and sea caves at La Jolla Cove, and the bluffs of Torrey Pines. Inland lie the forested Cuyamaca and Laguna mountains and the canyons of Anza-Borrego.

San Francisco's is greener and wilder, in the cool, foggy way of the north: the cliff path at Lands End, the Marin Headlands just across the bridge, the redwoods of Muir Woods and the elephant seals of Point Reyes. Go to San Diego for the water and the desert, and to San Francisco for hiking and big views.

San Francisco has the stronger day trips, and wine country is the main reason. Napa and Sonoma are about an hour north. Ferries cross to Sausalito, Berkeley is a short train ride away, and Monterey and Carmel make a fine longer day down the coast.

San Diego's list is unusual rather than deep. Mexico is close, with Tijuana reached by trolley and the Valle de Guadalupe vineyards further south. Temecula, Julian and the North County beach towns are easy outings. Most of them need a car, and neither region has much in the way of old towns.

San Diego is one of the best family destinations anywhere. The zoo in Balboa Park, the Safari Park, SeaWorld on Mission Bay and Legoland in Carlsbad could fill a week. Calm bay beaches and a mild climate make outdoor days easy. The cost is the driving between them, so expect one big attraction a day.

San Francisco works best for children who like science. The Exploratorium and the California Academy of Sciences are excellent, and the cable cars and the sea lions at Fisherman's Wharf add some fun. But the hills are hard going with a pushchair, the sea is too cold for paddling, and there is no theme park.

San Francisco is much easier without a car. The city is only about 11km across, and one Clipper card covers Muni, BART, the cable cars and the bay ferries. The real obstacle is the hills, not the distances.

San Diego is walkable only downtown, in the Gaslamp, Little Italy and along the waterfront, with the trolley running out to Old Town and the border. The beaches, La Jolla and the big family parks are far apart and the buses are slow. Most visitors hire a car and then struggle to park at the beach.

San Francisco shops better, mainly because its neighbourhoods have character: design boutiques in Hayes Valley, bookshops and vintage on Valencia Street, Fillmore Street and the Haight, with Union Square for the department stores. San Diego relies more on malls, with Fashion Valley and the outlets by the border, plus independent shops in North Park and Little Italy and Mexican crafts in Old Town. Neither is worth choosing for shopping alone.

Neither city is cheap, but San Diego is easier on a budget. Its hotels and meals are costly and the big family attractions charge high admission. Even so, taco shops, taprooms, free beaches and the gardens of Balboa Park make a frugal day possible.

San Francisco is among the most expensive cities in the country, with hotel rates that climb during big conferences and steep prices for drinks. What helps is that you do not need a car, and the parks, the walk across the bridge and the coastal trails cost nothing.

San Francisco has the deeper programme. San Francisco Opera and San Francisco Ballet share the War Memorial Opera House, the symphony plays a full season at Davies Hall, the American Conservatory Theater stages serious drama, SFJAZZ is a home for jazz and the Fillmore carries rock history.

San Diego's strength is theatre, and it is a real one: both the Old Globe and La Jolla Playhouse have sent shows on to Broadway. Beyond those, the symphony's summer season on the waterfront and a short opera season make for a good evening, but not a reason to travel.

Neither city has a bathing tradition, so the difference is one of kind. San Diego relaxes you through its pace: resort spas in La Jolla, Coronado and Carlsbad, the yoga culture of Encinitas and slow beach-town mornings in warm weather.

San Francisco has a Japanese-style bathhouse in Japantown and real hot springs within reach at Calistoga, known for its mud baths. The city itself feels more hurried, though, and you find calm in the Japanese Tea Garden or the foggy outer neighbourhoods.