San Diego or Scottsdale?

This is the widest gap between the two. San Diego has around 110km of coast, from the broad sand at Coronado and the boardwalk shared by Mission Beach and Pacific Beach to the gentle surf at La Jolla Shores. Mission Bay has calm, sheltered water where small children can paddle. The sea is cool for much of the year, but you are on the coast.

Scottsdale is in the Sonoran Desert with no coast at all. Swimming means the resort pool. For an outing there are the desert lakes, such as Saguaro Lake and Canyon Lake, and in summer people float down the Salt River on inner tubes.

San Diego's food has more character of its own. Being so close to the border gives it Baja fish tacos, carne asada burritos and taco shops that stay open late. Convoy Street adds a long run of Asian kitchens, and North Park and Miramar sit in one of the country's densest craft-beer scenes.

Scottsdale's Old Town is more polished than distinctive, with steakhouses, patio grills and long brunches aimed at golfers and groups. Its most local food is Sonoran Mexican, with plate-sized flour tortillas and green chile, and many of the more interesting places to eat are in Phoenix.

Neither is a great museum city, but San Diego has more to fill your days. Balboa Park brings together its art, natural history and air and space museums among Spanish Colonial Revival buildings. The USS Midway, the adobe buildings of Old Town and Mission San Diego de Alcalá, the first of California's missions, add history that Scottsdale cannot match.

Scottsdale's standout is Taliesin West, Frank Lloyd Wright's desert studio, and there is frontier art at Western Spirit and plenty of galleries selling Native American work. For the Heard Museum or the Musical Instrument Museum you cross into Phoenix.

Bars close at 2am in both cities, and each has one loud, party-minded district, so the real difference is how spread out the nights are. San Diego divides them between the clubs of the Gaslamp Quarter, the student bar strip in Pacific Beach, and relaxed taprooms and cocktail bars in North Park and Hillcrest, which is also the centre of gay nightlife.

Scottsdale puts almost everything into a few blocks of Old Town. It is glossier and more dressed-up there, with bottle service and rooftop lounges, and it gets much busier in spring. Away from Old Town, evenings are quiet and spent at the resort.

Both are outdoor places, but San Diego has more variety and works in every season. On the coast you get ocean bluffs at Torrey Pines, sea lions and sea-cave kayaking at La Jolla, surfing and whales passing in winter. Inland there is mountain forest and then the Anza-Borrego desert.

Scottsdale's strength is the desert on its doorstep. There are saguaro trails in the McDowell Sonoran Preserve, steep climbs up Camelback Mountain and longer routes in the Superstition Mountains, as well as balloon flights and golf. In summer the heat limits hiking to the hours around dawn.

San Diego's outings are more varied, mainly because Mexico is next door. You can reach Tijuana by trolley and a walk across the border, or drive further south to the Valle de Guadalupe vineyards. On the US side there is Temecula wine country, the hill town of Julian with its apple pie, and beach towns along the coastal rail line.

From Scottsdale the classic day out is north to the red rocks of Sedona, stopping at Montezuma Castle and the old mining town of Jerome. Tucson and the San Xavier mission lie to the south. The Grand Canyon really needs an overnight stay.

San Diego is one of the easiest family destinations anywhere. The zoo in Balboa Park, its Safari Park near Escondido, SeaWorld on Mission Bay and Legoland in Carlsbad could fill a week. The mild weather and calm paddling beaches make the days in between easy too.

In Scottsdale, families mostly come for the resorts, with their lazy rivers, water slides and kids' clubs. In town there is the miniature railway park, and the aquarium and butterfly house are just outside. In summer the heat drives children indoors or into the water from midday.

San Diego is the easier of the two to manage without a car, at least in the centre. Downtown, Little Italy and the waterfront are easy on foot, the trolley runs to Old Town and the border, and coastal trains go up to the beach towns. La Jolla and the big parks are still far apart, and buses to them are slow.

Scottsdale is built for driving. It is a long, narrow city of wide main roads, and the regional light rail does not reach it. Old Town is walkable and has a free trolley, but beyond it you drive. At least driving is easy, on a simple grid with plenty of parking.

Scottsdale is the better place to shop. As well as its big luxury mall, it has the gallery district on Main Street and Marshall Way, and dealers nearby sell southwestern painting, Navajo and Hopi silver, turquoise, Pueblo pottery and western boots. The quality at the better ones is high.

San Diego has Fashion Valley for luxury brands and a large outlet centre by the border. Its more personal finds are the vintage and design shops of North Park and Little Italy, Mexican crafts in Old Town and surf gear almost everywhere.

Scottsdale is slightly kinder to a budget, mainly because of its calendar. Its resorts cut their rates sharply in the hot summer, and motels along the main roads and Mexican food help keep costs in check. Hiking in the desert costs nothing.

San Diego is expensive all year, and beach hotels cost the most in summer. The zoo, SeaWorld and Legoland all charge high admission, and you pay for parking on top. Free beaches, taco shops and the gardens of Balboa Park are the main ways to save.

San Diego has the stronger stage of its own. The Old Globe in Balboa Park and the La Jolla Playhouse are serious theatre companies that have sent shows to Broadway, and the symphony plays a summer season on the bay.

Scottsdale has its performing arts centre in Old Town and the concert theatre at the Musical Instrument Museum for world and acoustic music. For symphony, opera, ballet or touring Broadway shows, you head into Phoenix or Tempe.

Scottsdale is built for this. Its large resort spas offer desert-inspired treatments, outdoor pools and steam rooms, and many are open to day guests. The dry air and mountain views set a pace of golf, long lunches and early nights.

San Diego relaxes in a different way, through mild weather, sunset walks and slow beach-town mornings. It has resort spas in La Jolla, Coronado and Carlsbad and a long-standing yoga culture in Encinitas. Neither city has historic baths or public bathhouses.