Aspen or Sun Valley?

Neither is a place to swim, and both leave you with cold mountain water or a heated pool. They differ in what the water offers. Sun Valley has an actual sandy shore at Redfish Lake under the Sawtooths, about an hour's drive away, which makes for a fine summer afternoon even if few people go in deep. Aspen's water is more about the river, with rafting on the Roaring Fork and small reservoirs close to town.

Aspen eats better and more widely. Its downtown grid holds polished chef-led restaurants, Italian kitchens and sushi counters, its après-ski terraces at the foot of Aspen Mountain are part of the day, and each June the Food & Wine Classic brings in chefs and winemakers.

Ketchum has a good number of restaurants for a small place, with a regional leaning towards Idaho trout, lamb and elk, but beyond a few ambitious kitchens it is mostly grills, pizza and breakfast spots. In both towns cheap meals are scarce and the quiet seasons thin out the choice.

Neither has major sights, but Aspen gives you more to look at. Its silver-boom downtown keeps red-brick Victorian blocks around the Wheeler Opera House, the West End has painted miners' cottages, and the Aspen Art Museum and Herbert Bayer's modernist Institute campus add a design interest.

Sun Valley's story is shorter and more specific: the 1936 resort built by Union Pacific with the world's first chairlifts, the film-star photographs in the lodge corridors and Hemingway's grave in Ketchum. It is an interesting hour or two rather than an afternoon's walk.

Aspen has a real night out in winter. Après-ski moves from the slopeside decks into the downtown bars and lounges, and over Christmas, New Year and the X Games a well-dressed crowd keeps the hotel bars and a few small clubs busy late. Summer evenings are gentler, with drinks on patios.

Ketchum's scene is smaller. It has a handful of saloons, wine bars and hotel lounges, a band on a busy winter weekend and a couple of old western bars that stay loud until closing, but no clubs at all. Outside the ski season and midsummer, both towns go quiet and many places close.

Both are first-rate mountain bases and the difference is in character. Aspen offers variety: four ski areas from gentle Buttermilk to steep Highlands and vast Snowmass, then in summer the Maroon Bells, high passes and summits above 4,000m straight from the valley.

Sun Valley concentrates on one great mountain, Bald Mountain's long, uninterrupted fall-line runs, with dry snow, groomed Nordic trails and dense singletrack in summer. Its wild hinterland stands out, with the Sawtooths, Salmon River rafting and Silver Creek's spring-creek fly fishing all within reach.

Aspen has more towns within reach. Glenwood Springs, about an hour down the valley past ranching and arts town Carbondale, has a historic railway-era centre. From Carbondale, a side trip up the Crystal River valley leads to Redstone's coke ovens and the old quarry village of Marble. In summer, Independence Pass opens the road to Leadville's Victorian main street, though the pass closes in winter and the list gets shorter.

From Sun Valley, most outings head into empty country rather than to other towns. Hailey's small main street and the log-cabin outpost of Stanley beyond the Sawtooths are the nearby options. Shoshone Falls on the Snake River is about two hours south, and Boise is too far for an easy day.

Aspen works better with children because it gives you two good learning mountains, Buttermilk and Snowmass, both with kids' areas, plus summer lift rides, alpine coasters, ropes courses and downtown fountains. Sun Valley has a sensible beginner hill away from the main mountain and plenty of summer activities, from horse rides to an outdoor ice rink, but rainy days and non-skiing teenagers are harder to manage. Neither has a zoo or theme park, and altitude can tire small children in both, with Sun Valley's midwinter cold adding to that.

Aspen is the easier place without a car. Free buses connect all four ski areas, a valley line runs to Glenwood Springs, a summer shuttle reaches the Maroon Bells, and the airport is minutes from town.

Sun Valley handles a ski week well on foot, by free bus and along the valley bike path, but almost everything beyond the lift bases needs a car. The Sawtooths, the hot springs and the fishing are reached by long roads with no buses, and the larger airports are a long drive away.

Aspen is a genuine luxury shopping town, with international designer boutiques, jewellers, high-end ski wear and fur along its pedestrian malls. Ketchum is smaller and more practical, with good ski, fly-fishing and outdoor gear shops, western art galleries and a few cashmere and home-decor boutiques for second-home owners. Neither suits a browser looking for markets or bargains.

Both are among the most expensive mountain trips you can take, with rooms, meals and lift access priced for wealthy visitors. The way to save differs slightly. Aspen has Glenwood Springs and Carbondale down the valley as cheaper bases on a bus line, while Sun Valley's quiet spring and autumn months and lodging further down the valley ease the cost a little.

Aspen has more going on, and for longer. The Aspen Music Festival fills about eight weeks with orchestral, chamber and opera performances in the Benedict Music Tent, alongside jazz, the Aspen Santa Fe Ballet and Institute talks, and the Wheeler Opera House programmes concerts and comedy all year.

Sun Valley's free summer orchestra on the lodge lawn is a lovely picnic evening, and its tradition of star skaters performing on the outdoor rink is all its own. Outside summer, though, there is almost nothing to see.

Both offer resort spas and calm once the busy weeks pass, and the difference is in how you soak. Aspen's big hot springs are at Glenwood Springs, an hour away, with developed mineral pools and cave vapour baths, or high up at Conundrum after a long hike.

Sun Valley's soaking is closer and wilder: steaming heated pools at the resort and undeveloped creekside springs up the Warm Springs valley. Its quieter evenings also make it more restful in peak season than Aspen.