Fort Collins or Sun Valley?

Neither is a beach destination, and in both places summer swimming means fresh water in July and August. The difference is the water temperature. Horsetooth Reservoir, just west of Fort Collins, warms up enough for lazy afternoons among the paddleboards. Sun Valley's best swim is Redfish Lake under the Sawtooths, an hour's drive away and cold even in midsummer, so its heated outdoor pools are the more reliable choice.

Fort Collins eats and drinks better, mainly because of its beer. Its long-established breweries run tours and its taprooms are spread across the city, enough to fill several days. Old Town adds gastropubs, taco spots, a few farm-to-table kitchens and summer farmers' markets selling Palisade peaches.

Sun Valley's restaurants are mostly in Ketchum and are aimed at a wealthy second-home crowd. They range from après-ski grills to a few serious kitchens cooking Idaho trout, lamb and elk. That is good for a town this small, but the choice is narrower, cheap meals are scarce and some places shorten their hours in spring and autumn.

Neither town is a sightseeing trip, but Fort Collins has a little more to see. Its red-brick and sandstone Old Town, the Museum of Discovery, the Victorian Avery House and the university's art museum make a full but gentle day.

Sun Valley's interest lies in its story. The Union Pacific railroad built it in 1936 as America's first destination ski resort. The lodge's corridors of film-star photographs recall that era, and Hemingway's grave is in the Ketchum cemetery. An afternoon covers it.

Fort Collins is the place for an evening out. Its large university fills the pubs, rooftop patios, cocktail bars and taprooms around Old Town's square on weekends, although the scene stays casual and there are few dance clubs.

In Sun Valley, nights out mean après-ski. That is a drink in a Ketchum saloon, wine bar or hotel lounge after the lifts close, perhaps with a band on a busy winter weekend. There are no clubs, and outside the ski season and midsummer most evenings end soon after dinner.

Both are outdoor towns, but Sun Valley is the purer mountain destination. Bald Mountain rises straight out of Ketchum, with long, steep runs and a separate gentle hill for beginners, and the Sawtooths lie an hour north. In summer the hills become a dense network of singletrack, and there is fly fishing on Silver Creek and rafting on the Salmon River.

Fort Collins sits where the plains meet the foothills rather than up in the mountains. That shows in winter, when there is no downhill skiing nearby, only snowshoeing and cross-country. The rest of the year it still offers plenty: Horsetooth Mountain and Lory State Park are a short drive west, the Poudre canyon has rafting and fishing, and Rocky Mountain National Park is about an hour and a half away.

Fort Collins is much better placed for visiting other towns. Boulder beneath the Flatirons, Denver's big museums, Estes Park, Golden and Cheyenne's frontier museum are each about an hour or a little more by car.

Sun Valley is surrounded by wild country, so most days out head into the mountains rather than to towns. The nearest places are Hailey, with its small historic main street, and Stanley, a log-cabin outpost beyond the Sawtooths. Shoshone Falls is about two hours away, and Boise is too far for an easy day.

Both are safe, unhurried places with children, and neither has a zoo or theme park in town. Fort Collins has more to fill a week: the Museum of Discovery with its dome theatre, the farm animals at Lee Martinez Park, flat cycle paths along the river and summer days at Horsetooth. Denver's bigger attractions are also within reach.

Sun Valley works best for families who ski, thanks to its separate beginners' hill and well-run ski school, and in summer there are horse rides, fishing and an outdoor rink. Rainy days are hard to fill, though, and the altitude and midwinter cold can be tough on toddlers.

In both places the centre is easy without a car and anything beyond it is hard. Fort Collins gets around by bike and a rapid-bus line. It is one of the most bike-friendly cities in the country, with protected lanes, bike-share and long trails linking Old Town, the campus and the breweries.

In Sun Valley, a free bus links Ketchum, the resort village and the lift bases, so you can spend a ski week without driving. The catch is getting there: the airport in Hailey is small, and the larger airports are a long drive away on roads that can be snowy in winter.

Neither is a shopping destination, but the browsing is different. Fort Collins's Old Town has independent bookshops, vintage clothing, cycling gear and Colorado-made gifts, with a mall and highway chains beyond. Ketchum's few blocks are more upmarket, with western and fine art galleries, cashmere and western-wear boutiques and well-stocked ski and fly-fishing shops, all at high prices.

The gap in cost is wide. Fort Collins is mid-priced for an American city, which is not cheap by world standards, but chain hotels and motels along the highways and casual taprooms keep a stay within reach. Its foothills trails, river paths and Old Town cost nothing, so a hire car is usually the biggest extra, and rooms only jump on graduation and football weekends.

Sun Valley is very expensive. Its wealthy second-home community sets what you pay for a bed, a dinner in Ketchum and a day on the mountain, and there is little budget lodging in the valley. A winter trip also means paying for lift access, a cost a winter in Fort Collins avoids because there is no downhill skiing nearby. Staying further down the valley, coming in the quiet spring or autumn months and using the free local buses all help, but the same week still costs far more than in Fort Collins.

Neither town has a lot of live performance, but the two calendars are very different. Fort Collins has something on for most of the year. The Lincoln Center hosts touring Broadway, dance and the local symphony, the university's arts centre stages opera and theatre during term, and indie and bluegrass bands play Old Town's small stages.

Sun Valley packs nearly everything into summer. A professional orchestra plays free symphony and chamber concerts in the pavilion by the lodge, and skaters perform on the outdoor rink. The rest of the year there is very little.

Sun Valley is the better place to unwind. The resort and the larger hotels have full spas and outdoor heated pools, which are at their best under falling snow. Up the Warm Springs valley, rough hot springs beside the creek offer a wilder soak.

Fort Collins has no hot springs nearby. The closest is at Idaho Springs, about an hour and three-quarters away, so wellness there means day spas, massage studios and yoga classes. The calm comes from its quiet neighbourhoods and shaded river paths rather than from anything built for rest.