Keystone or Mammoth Lakes?

Neither town has a coast, and swimming plays a small part in both. At Keystone, Dillon Reservoir is fed by snowmelt and is mostly closed to swimmers, so you can boat on it but the realistic way into the water is a pool or hot tub.

Mammoth Lakes at least offers a summer dip. In July and August people swim at Horseshoe Lake in the Lakes Basin, and lower Crowley Lake warms a little more, although the water is never warm. Hot Creek is off limits for bathing.

The two eat much alike: hearty ski-town food, burgers and pizza, a handful of more ambitious dinners and local craft beer. Keystone's menus lean on Colorado lamb, elk and trout, and its most memorable meal is reached by gondola at the summit.

The difference is where you go for more choice. From Keystone, Frisco, Dillon and Breckenridge are a short drive away. Mammoth Lakes is on its own, but it feeds a big winter crowd and has more variety than a town its size usually would, with tacos and steakhouses as well as big breakfasts. Some of its kitchens cut back in the quiet spring and autumn months.

Both are modern resorts with almost nothing to sightsee, so neither should be chosen for culture. What history there is takes different forms. Around Keystone, mining-era cabins and ruins survive along the Snake River valley above Montezuma. Mammoth Lakes has a small local history museum in a log cabin, and its real heritage sites lie an hour or more down the highway.

Neither is a place for a big night out, but Mammoth Lakes has a little more going on in town. Its brewery taprooms and pubs keep some locals drinking alongside the skiers, and long weekends in the ski season can run late.

Keystone's evenings are built around families and early starts. The decks at River Run are full at après-ski and the resort goes quiet soon after dinner. Its consolation is that Breckenridge's Main Street is a short bus ride away.

Both are first-rate mountain destinations, and the difference is what kind of mountains you get. Keystone works as a base for a whole cluster of ski areas. It has three peaks of its own, Arapahoe Basin a few minutes away and Vail within an hour. Summer brings Grays and Torreys Peaks and alpine tundra at Loveland Pass, and at about 2,800m it sits higher of the two.

Mammoth Lakes has a single, very large mountain whose season often runs into early summer, set in a stranger, volcanic landscape. You get granite-ringed lakes, the basalt columns of Devils Postpile, the tufa towers of Mono Lake, and over Tioga Pass in summer the Yosemite high country.

Keystone has far more within easy reach. Breckenridge is about half an hour away. Across the Continental Divide are Georgetown and its historic loop railway and the old mines of Idaho Springs. Leadville's mining-boom streets and Vail's village are also close, and Denver's museums are a long drive away when you want a city.

From Mammoth Lakes the outings are fewer and spread along one highway. Still, they are memorable: the gold-rush ghost town of Bodie and the internment camp at Manzanar are both worth the hour or so in the car. In winter the passes over the Sierra close, and the choice narrows further.

Keystone is better set up for children. The family ski trip is its core business, with a big ski school and tubing. In winter there is a snow fort on the mountain and a huge skating rink on the frozen lake at Lakeside, and free shuttles take a lot of the effort out of getting around.

Mammoth Lakes suits families who already love the outdoors. They can row and fish for trout in the Lakes Basin, and older children can try the bike park. It has nothing for a bad-weather day, though, and reaching the trailheads usually means driving.

Keystone is easier without a car once you arrive. Free shuttles link its three bases, and free county buses run to Dillon, Silverthorne, Frisco and Breckenridge. The weak point is getting there over I-70 from Denver in winter traffic.

Mammoth Lakes is spread along a few roads, with only the pedestrian Village built for walking. Winter shuttles, the gondola and the summer trolley to the Lakes Basin cover a ski or lake trip. Beyond that the Eastern Sierra really needs a car.

Keystone has the edge thanks to its neighbour. Silverthorne's large outlet centre, about ten minutes away, draws shoppers from across the county looking for brand-name clothes and outdoor wear. In the resort itself, River Run sells ski gear and gifts.

Mammoth Lakes has nothing comparable. Its strength is specialist kit: good climbing and fly-fishing shops, plus galleries selling Sierra landscape photography.

Both are costly, but Mammoth Lakes gives you more ways to spend less. Its summer of hiking, lakes and scenic drives costs little beyond a park pass, and rooms soften in spring and autumn, though groceries carry resort prices.

Keystone stays expensive in every season, and it is at its dearest over Christmas, New Year and spring break. Free buses, condo kitchens and supermarkets in Dillon and Silverthorne take some of the edge off.

Keystone has more to choose from, mostly because of its neighbours. In summer there are concerts at Dillon's amphitheatre by the reservoir and Breckenridge's long-running classical festival at the Riverwalk Center. All year round, a professional theatre company plays in Silverthorne.

Mammoth Lakes keeps things local and modest. A community theatre company performs on the college campus, and summer brings a jazz festival, chamber music and concerts in meadows with the mountains behind.

Mammoth Lakes is the better place to unwind, and its volcanic ground is the reason. Natural hot springs sit in open sagebrush facing the Sierra. They are simple pools with no facilities and can be busy at sunset, and there are lodge spas in town too.

Keystone's version of wellness is recovery after skiing: a massage at a resort spa or a hot tub under falling snow. For natural springs you have to drive to Idaho Springs or as far as Glenwood Springs.