Las Vegas or Sun Valley?

Neither place has a coast, and neither is worth visiting for swimming, but the water you do find is very different. Around Las Vegas it is warm: Boulder Beach on Lake Mead has a gravel shore in a shadeless desert basin, and the resort pools along the Strip add wave pools and lazy rivers for hot afternoons.

Sun Valley's swimming is cold and scenic. The sandy shore of Redfish Lake under the Sawtooths is an hour away and chilly even in August, so heated outdoor pools are the reliable option.

Las Vegas eats on a much bigger scale. The Strip has steakhouses, French dining rooms, tasting menus and buffets, and the kilometres of Asian restaurants along Spring Mountain Road plus the suburban Mexican cooking give it real depth away from the resorts.

Ketchum has a lot of restaurants for a small town, and Idaho trout, lamb and elk give the better ones a local flavour Las Vegas lacks. Still, the choice is that of a resort village, cheap meals are rare, and some kitchens cut back their hours in the quiet seasons.

Neither is a sightseeing destination, but Las Vegas gives you more to look at. The themed resorts, the fountains and the Fremont Street light canopy fill an evening, and the Neon Museum's sign yard and the Mob Museum in the old federal courthouse tell the city's story properly.

Sun Valley's history fits into an afternoon: the 1936 lodge built by the railroad, the world's first chairlifts, the film-star photographs in the corridors, and Hemingway's grave in Ketchum cemetery.

This is where the two differ most. Las Vegas never closes. Resort superclubs and dayclub pool parties run all weekend, and downtown and the arts district offer cheaper cocktail lounges and craft beer for those who would rather skip the dress codes.

Sun Valley's evenings are après-ski in a handful of Ketchum saloons and wine bars, with perhaps a band on a busy winter weekend. Out of season most nights end soon after dinner.

Las Vegas has impressive desert close by: the sandstone cliffs and climbing of Red Rock Canyon, the flame-coloured rock of Valley of Fire and the cooler pine forests of Mount Charleston. However, the summer heat restricts it to dawn outings for months at a time.

Sun Valley is built around the outdoors in every season. Ski runs drop straight into town, singletrack and Sawtooth trails take over in summer, and fly fishing, rafting on the Salmon River and golden aspens in autumn complete the year.

Both are isolated, but Las Vegas has the better single outing: Hoover Dam and the tidy workers' town of Boulder City make an easy half day. The Grand Canyon and Zion trips sold on the Strip are long drives to landscapes.

From Sun Valley the nearest places are small: Hailey's old main street, the log-cabin outpost of Stanley in a superb setting, and Shoshone Falls two hours south. Most days out here head into the mountains.

Sun Valley is the easier place to bring children. The gentle beginners' hill and ski school, bike paths, horse rides, the outdoor rink and quiet streets make for a relaxed week. However, there are no attractions built just for children, and rainy days or teenagers who don't ski can be a problem.

Las Vegas has the attractions Sun Valley lacks, including an indoor amusement park, a shark aquarium and a children's museum. But children cannot linger on the casino floors that every route passes through, and the adult side of the Strip is hard to avoid.

Getting around is fairly similar in both, though Sun Valley is a little easier. Ketchum is small and flat, and a free bus and valley bike path link town, village and lifts, so many skiers never drive. The Strip looks walkable, but its giant resorts, footbridges and summer heat send most visitors to taxis, the monorail or round-the-clock buses.

Either way, the landscapes need a hire car, whether for Red Rock and Hoover Dam or for the Sawtooths and the hot springs.

Las Vegas is a serious shopping stop. The resort malls hold the big fashion and jewellery houses, the Fashion Show mall adds department stores, and two outlet centres attract bargain hunters. There is little that is local, though.

Ketchum is the reverse: a few blocks of western art galleries, fly-fishing and ski shops and upmarket boutiques. It has character but the range is small, and it is no place for a shopping spree.

Neither is cheap, but Las Vegas leaves far more room to save. Midweek rooms on and near the Strip, and cheaper ones downtown, can be good value, and meals in Chinatown cost much less than the resorts. Weekends, resort fees and nights out push the bill up quickly.

In Sun Valley, the wealthy second-home community sets the price of rooms, meals and lift access, and there is little budget lodging. Staying down the valley in spring or autumn only takes the edge off.

Las Vegas offers live entertainment every night of the year: acrobatic water shows, magicians, comedians and pop stars on long residencies. The Smith Center adds touring musicals and the Philharmonic.

Sun Valley's season is short but charming. In summer a professional orchestra gives free concerts in the pavilion by the lodge while people picnic on the lawn, and skaters perform on the outdoor rink. For the rest of the year there is very little.

Sun Valley is the more restful of the two. Outdoor heated pools are especially good under falling snow, the rough natural hot springs up Warm Springs creek feel nothing like a spa, and the evenings are quiet.

Las Vegas has bigger spas, with thermal circuits, salt rooms and ice rooms open for a day fee. But casinos that never sleep surround them, so relaxing there means a non-gaming hotel and an early booking.