Phoenix or San Diego?

This is the widest gap between the two. Phoenix is a desert city several hours from the ocean, so swimming means resort pools with lazy rivers, the small beaches at Saguaro and Canyon lakes among bare cliffs, or tubing down the lower Salt River in summer.

San Diego is built along its coast, with Coronado's broad strand, the surfers and volleyball of Mission and Pacific beaches, and quieter cliff-backed sand in Del Mar and Encinitas. The Pacific stays cool for much of the year, but Mission Bay's sheltered water gives small children an easy paddle that Phoenix cannot match.

Both cities eat best at the Mexican end of the menu, though from different sides of the border. Phoenix has Sonoran cooking, with machaca, carne asada, paper-thin flour tortillas and bacon-wrapped hot dogs from evening carts, plus a strong name for wood-fired pizza, but good meals are spread out and usually mean a drive.

San Diego has the edge thanks to its range and its setting. Baja fish tacos and California burritos come with fresh seafood by the water, Convoy Street adds a long run of Asian kitchens, and the craft breweries of North Park and Miramar give the city a drinking speciality Phoenix lacks.

Neither city has deep historic streets, but San Diego gathers its culture far more conveniently. Balboa Park puts the art museum, the Museum of Us, natural history and air and space among Spanish Colonial Revival buildings in one place, and the USS Midway, Old Town's adobes and the first California mission fill out a second day.

Phoenix has two standout reasons to visit, the Native American collection at the Heard Museum and Frank Lloyd Wright's Taliesin West, along with the Musical Instrument Museum. Beyond those its heritage is thin, and every sight is a separate drive.

The two are close, and they even share a pattern: a loud club district, a student strip and quieter neighbourhood bars, all closing at 2am. Phoenix's version is spread across separate towns, with Old Town Scottsdale's dance floors, Tempe's Mill Avenue and the craft beer bars of Roosevelt Row, so a night means choosing one and taking a ride-hail. In summer much of it moves onto patios with misters and resort pool parties.

San Diego's equivalents are the Gaslamp Quarter's rooftops and clubs, the beach-town bars of Pacific Beach, and brewery taprooms in North Park. Hillcrest also gives it a recognised centre for gay nightlife.

Both are strong outdoor cities, but San Diego wins on variety and season. Phoenix has rocky desert mountains inside the city, from South Mountain to the scramble up Camelback and the saguaro trails of the McDowell Sonoran Preserve, with Sedona's red rock within reach. In summer, though, the heat closes the trails by mid-morning.

San Diego works all year, and it adds the ocean to the desert. You can walk the bluffs at Torrey Pines, kayak into La Jolla's sea caves past sea lions and watch grey whales in winter, then drive an hour to pine forest in the Laguna Mountains or the badlands of Anza-Borrego.

San Diego has the more interesting list, largely because Mexico is so close. You can reach Tijuana by trolley and on foot, and the Valle de Guadalupe vineyards, Temecula wine country, apple-pie Julian and the beach towns up the coast by train make easy days out.

From Phoenix, Arizona's long distances shorten the choice. The hillside mining town of Jerome, Prescott's Western square, the cliff dwelling at Montezuma Castle and Tucson's mission all work, but each needs a car, and the Grand Canyon is too far for a comfortable day.

San Diego is one of the easiest cities anywhere to bring children to, and this is where it pulls furthest ahead. The zoo and Safari Park, SeaWorld on Mission Bay and Legoland in Carlsbad give it a week of big outings, the beaches and Balboa Park's lawns fill the gaps, and the mild weather means plans rarely fall through.

Phoenix covers the basics with its zoo, science centre, water parks and resort pools with slides, and spring training baseball in March makes a relaxed outing. It only works in the cooler months, though, since summer heat limits young children to early mornings, and every attraction involves a long drive.

Without a car, Phoenix gives you very little. The light rail is useful along one corridor, linking the airport with downtown Phoenix and Tempe, but Old Town Scottsdale, the resorts and the desert trailheads all lie well beyond it, and the buses are too slow to fill the gap. The few walkable patches are small, and summer heat makes them smaller still, so most visitors rent a car. The consolation is that the roads are easy and parking is simple.

San Diego lets you do far more on foot and by rail. You can spend whole days between the Gaslamp Quarter, Little Italy and the waterfront without driving, take the trolley to Old Town or the border, and ride the coastal train to the beach towns. You will still need a car or ride-hail for La Jolla, the Safari Park and Legoland, and beach parking is tight on summer weekends.

Phoenix comes out slightly ahead, mainly thanks to one buy San Diego cannot match: Navajo and Zuni silver and turquoise, Hopi katsina carvings and pottery from museum shops and reputable galleries. Scottsdale adds a large luxury mall and Western wear shops.

San Diego is mostly malls and browsing, with Fashion Valley for the big brands, a border outlet centre, and independent boutiques and vintage shops in Little Italy and North Park. Mexican pottery in Old Town and the surf shops are its closest thing to a local purchase.

Phoenix is the cheaper stay, particularly if you can handle the heat: resort rooms that are expensive from January to April fall sharply in summer, and freeway chain hotels are good value all year. Hiking costs nothing, and the main extra expense is a hire car.

San Diego is expensive in every season, with costly beach and downtown hotels, tax and tip on every meal, and high admission at the zoo, SeaWorld and Legoland. Free beaches, taco shops and Balboa Park's gardens help, but it never feels like a budget trip.

San Diego has the stronger stage. The Old Globe in Balboa Park, with its outdoor Shakespeare stage, and the La Jolla Playhouse both produce their own work and have sent shows on to Broadway. In summer the symphony plays outdoors by the bay.

Phoenix has the usual institutions, including the symphony, opera, ballet and touring shows at Wright's round Gammage auditorium in Tempe. Its most distinctive venue is the small concert hall at the Musical Instrument Museum, and its seasons go quiet in the summer heat.

Phoenix is the better place for a dedicated rest. The large desert resorts along Camelback Mountain and through north Scottsdale combine full spas, sage and clay treatments, golf and several pools, and the dry winter sun makes a week by the water easy, though the best of it costs resort money.

San Diego relaxes you through its pace more than its spas. There are resort spas in La Jolla, Coronado and Carlsbad, Encinitas has a long-standing yoga and meditation scene around its clifftop gardens, and sunset walks by the sea do much of the rest. Neither city has a tradition of public baths or hot springs.