Aspen or Keystone?

Neither town is for swimmers. Aspen's water is the Roaring Fork River and some small alpine lakes, better for rafting than a swim. Keystone looks down on the wide Dillon Reservoir, which is good for boating but mostly closed to swimming. In both places, the hotel pool or hot tub is where you actually get wet.

Aspen is a place to eat out, while Keystone is a place to eat after skiing. Aspen's few downtown blocks support more ambitious cooking than a town its size has any right to, with serious kitchens and cellars pitched at the winter crowd, and every June the Food & Wine Classic gives it a name well beyond the mountains. What it lacks is a middle ground: there is little casual or cheap, and in the quiet spring and autumn weeks many kitchens simply shut.

At Keystone, meals are built around the lift bases, filling and convenient rather than memorable. Local game, trout and Colorado craft beer give it some character, and a gondola ride up to the summit makes for a special dinner. Most guests count the condo kitchen as part of the plan, and anyone who wants more choice drives down to Frisco or Breckenridge.

Aspen at least has a past you can see. Its silver-boom downtown keeps red-brick Victorian blocks around the Wheeler Opera House, and the West End has painted miners' cottages. The Aspen Art Museum and Herbert Bayer's modernist Institute campus add something more recent. Together they fill an afternoon.

Keystone was built for skiing in the 1970s, and River Run Village is convenient rather than interesting. Its history survives in cabin ruins up the Snake River valley, and for museums you have to go to Breckenridge or further.

Aspen is the place for a night out. In ski season, après-ski moves from the slopeside decks into downtown bars, lounges and a few small clubs. Around Christmas, New Year and the X Games they stay busy late with a well-dressed crowd. Summers are calmer, and the shoulder seasons are quiet.

In Keystone, the evening is an hour of après-ski at River Run with skiers still in their boots, then an early night before first chair. For anything livelier, guests take the bus to Breckenridge's Main Street.

Both are first-rate mountain bases, and the difference is in kind. Aspen's four mountains range from gentle Buttermilk to steep Highlands, the gondola rises straight from downtown and summer opens the Maroon Bells and the wilderness of the Elk Mountains. Keystone sits higher, at about 2,800m, with bowls above 3,600m. Arapahoe Basin is just up the road and Breckenridge, Copper Mountain and Vail are within an hour, so it is easier to ski several resorts in one week.

In summer, Keystone adds sailing and paddleboarding on Dillon Reservoir and the climbs up Grays and Torreys Peaks. Aspen has rafting and fly-fishing on the Roaring Fork and the drive over Independence Pass.

Keystone is better placed for days out. Breckenridge's Victorian centre is about half an hour away. Over the Continental Divide, Georgetown and Silver Plume are joined by a historic loop railway, and Leadville and Vail are within easy reach. Denver's museums are about an hour and a half away when the traffic allows.

From Aspen, the valley leads mostly to small places: Carbondale, Glenwood Springs, the quarry village of Marble and the ghost town of Ashcroft. Leadville is reachable over Independence Pass only in summer, and with the pass closed in winter the list gets short.

Keystone is the more family-minded resort. Beginner slopes on the lower mountain, a big ski school, tubing, a snow fort and a huge skating rink on the frozen lake keep children busy. Condos with kitchens close to the lifts make travelling with children simpler.

Aspen also works for a ski week with children, especially at Buttermilk and Snowmass, and in summer there are lift rides, alpine coasters and the environmental centre. Much of the town, though, is aimed at wealthy adults. In both places the altitude can tire young children for the first day or two.

Aspen is easier without a car. The downtown is a flat, compact grid with the gondola at its edge. Free buses run to all four mountains, a valley line goes to Glenwood Springs and the local airport is a few minutes away.

Keystone is spread over three bases, River Run, Mountain House and Lakeside, joined by free shuttles, and county buses run to Frisco and Breckenridge. The difficulty is getting there: there is no train, and the winter drive over I-70 from Denver can be slow, so many visitors hire a car. Aspen has its own drawback, as anywhere outside its valley means long mountain roads.

Aspen is a real place to shop, if you like luxury. A few downtown blocks hold international designer boutiques, high-end ski wear, jewellers, Western leather and art galleries, and wandering the pedestrian malls is part of an evening out.

Keystone's own shops are mostly gear, rentals and gifts in River Run Village. Its best option is the large outlet centre in Silverthorne, ten minutes away, which is better for practical brand-name outdoor clothing than anything in Aspen.

Neither is cheap, but Keystone costs somewhat less. Condos with kitchens and supermarkets in Dillon and Silverthorne make self-catering easy, the buses are free and summer is noticeably cheaper.

Aspen is among the most expensive places to vacation anywhere, with rooms, lift tickets and meals priced for a very wealthy clientele. Staying down the valley in Glenwood Springs or Carbondale helps, but not enough to make it a cheap trip.

In summer, Aspen is a serious music town. For about eight weeks the Aspen Music Festival fills the Benedict Music Tent with orchestral, chamber and opera performances, and you can picnic on the lawn outside and listen for free. Jazz festivals and the Aspen Santa Fe Ballet add more, and the Wheeler Opera House has shows all year.

Keystone depends on what is nearby: summer festivals on the village stages, concerts at Dillon's amphitheatre by the reservoir and Breckenridge's classical festival. Its main year-round option is the professional theatre company in Silverthorne, ten minutes away.

Outside ski season, Aspen is the more restful choice, with riverside paths, yoga in the parks and resort spas that offer altitude-recovery programmes. The big mineral pools and cave vapour baths of Glenwood Springs are an hour down the valley, and Conundrum Hot Springs is the reward for a long wilderness hike.

In Keystone, wellness means recovering after skiing: spa treatments and a hot tub at almost every lodge, best with snow falling. For natural hot springs you have to drive over the pass to Idaho Springs.