San Diego or Tucson?

This is the starkest difference between the two. San Diego has around 110km of shoreline: the wide flat sand at Coronado, the boardwalk at Mission and Pacific Beach, and quieter cliff-backed coves up through Del Mar and Encinitas. The water stays cool for much of the year, though, and is properly pleasant only in late summer.

Tucson is landlocked desert. The closest sea is the Gulf of California at Puerto Peñasco, a long weekend's drive, so cooling off means the resort pool or, after rain, the passing pools in Sabino Canyon.

Both cities eat in the shadow of the border, and the quality is much the same. The flavour differs, though. San Diego cooks Baja style, with fish and shrimp tacos, California burritos and fresh seafood, and it adds Convoy Street's run of Asian kitchens and one of the country's deepest craft-beer scenes.

Tucson's Sonoran cooking is meatier and more rooted: mesquite-grilled carne asada, paper-thin flour tortillas and the bacon-wrapped hot dog, best found in the old family places along South 12th Avenue. It also uses desert ingredients such as tepary beans and cholla buds, which you won't find on the coast.

San Diego has a little more to fill the days. Balboa Park gathers several sizeable museums among its exposition buildings, and the USS Midway, the historic ships of the Maritime Museum and Old Town's adobes extend the list along the bay.

Tucson's sights are fewer but more singular. Mission San Xavier del Bac, with its gilded interior, is arguably finer than anything in San Diego. The Arizona State Museum's Native American collections and the aircraft at Pima Air & Space are strong too, but two or three days covers the lot.

San Diego offers more choice after dark. The Gaslamp has rooftops and dance clubs, Pacific Beach has a rowdy beach-bar strip, and Hillcrest and North Park have cocktail bars, taprooms and the city's gay scene.

Tucson comes down to two walkable streets: Fourth Avenue's student dives and patios, and Congress Street's cocktail bars. It is easy-going and cheap, but clubs are scarce and summer is especially quiet.

Both are fine outdoor bases, and the difference is in the landscape. San Diego's outdoors is mostly coastal: sea lions at La Jolla Cove, kayaking into sea caves, tide pools at Cabrillo, surfing and the sandstone bluffs of Torrey Pines, with mountains and the Anza-Borrego desert an hour or more inland.

Tucson has the desert at its door. Saguaro National Park sits on both sides of the city, and the Mount Lemmon road climbs to pine forest and rock climbing. Serious road cycling and world-class birding round it out. The catch is summer, when the heat pushes hikes to dawn.

The two are evenly matched here, and both need a car for most outings. From San Diego the border is the draw, with Tijuana by trolley and the Valle de Guadalupe vineyards further south. Temecula's wine country, Julian's apple orchards and a train up the coast to the beach towns fill out the rest.

Tucson's outings head into frontier history instead: Tombstone, the mining town of Bisbee, the Tumacácori mission ruins and the grassland wineries of Sonoita, with Biosphere 2 to the north.

San Diego is one of the easiest cities anywhere to bring children to. Its zoo and Safari Park are world-class, SeaWorld and Legoland are close by, and the calm water of Mission Bay suits toddlers. Gentle weather in every month means plans rarely fall through.

Tucson works well with children from autumn to spring. The Arizona-Sonora Desert Museum, the old western film set and the giant aircraft are reliable hits. In summer, though, children are largely limited to resort pools and day trips up Mount Lemmon.

Neither city works well without a car, but San Diego is the less demanding. Its trolley ties downtown, Little Italy and Old Town to the border, and coastal trains reach the northern beach towns, even if La Jolla and the theme parks still mean driving. Tucson's single streetcar line covers only downtown and the university, and everything visitors come for lies on the edges. Its one consolation is that traffic is light and parking easy.

Neither is a shopping destination, and what they sell differs. San Diego has mainstream and upmarket shopping: luxury labels at Fashion Valley, outlets by the border, galleries in La Jolla and boutiques in Little Italy and North Park. Tucson is the place for things from the region, such as Native American jewellery, Tohono O'odham baskets and Mexican folk art. Its winter gem and mineral show is an event San Diego has nothing to match.

Tucson is noticeably easier on the wallet. Mid-range hotels cost less, cheap Sonoran food is everywhere, and summer brings real bargains for anyone who can take the heat. The car and the desert resorts are the main extra costs.

San Diego is expensive almost across the board. Beach and downtown hotels are dear, especially in summer, and the zoo, SeaWorld and Legoland all charge high admission. Free beaches and Balboa Park's gardens help, but only so much.

San Diego's stages carry more weight. The Old Globe and the La Jolla Playhouse are producing theatres that have sent shows to Broadway, and the symphony's summer concerts on the bay make a fine evening out.

Tucson's season is smaller and runs mainly from autumn to spring. It has a symphony, a shared opera company and touring shows at Centennial Hall, but its own character comes through in the small rock rooms on Congress Street and its deep mariachi tradition.

Tucson is the better place to switch off. It was one of the birthplaces of the American destination spa, and the long-established retreats in the Catalina foothills build whole stays around fitness, desert walks and meditation, all set in quiet and wide skies.

San Diego offers relaxation of a looser, beach-town kind. There are resort spas in La Jolla and Coronado and Encinitas has its yoga culture, but the pace of its busier districts is far from restful. Neither city has a public bathing tradition.