Chiang Rai or Kanchanaburi?

Neither town has a coast, and either needs a separate stop in the south if you want sand and salt water. The freshwater swimming is different in kind. Kanchanaburi has the more memorable option in the tiered turquoise pools of Erawan, where fish nibble your feet, plus lazy floats on the River Kwai from the raft houses. In Chiang Rai you swim in forest waterfall pools, a reservoir or a hotel pool.

Chiang Rai is the more rewarding place to eat, because it has a regional cuisine of its own. Khao soi, sour nam ngiao, sai ua sausage and chilli dips with sticky rice fill the night bazaar and walking-street markets. The surrounding hills supply a large café culture of local coffee and oolong, often served in gardens.

Kanchanaburi's cooking is honest central Thai food served at shophouse counters and the night market by the station. Its one local habit is eating river fish at open-air restaurants or on floating rafts at sunset. Neither town offers fine dining or much beyond Thai food.

Chiang Rai has more to see and a more unusual character. Its modern temple art, from the mirrored white plaster of Wat Rong Khun to the sapphire Blue Temple and the dark teak halls of Baan Dam, is unlike anything else in the country. Wat Phra Kaew, where the Emerald Buddha was found, adds some older history.

Kanchanaburi's sightseeing tells a single story: the building of the Thailand-Burma railway by prisoners and labourers in the Second World War. You can walk across the bridge, and the rows of graves at the war cemetery and the Railway Centre are deeply moving. Once you have seen them, though, there is little else, apart from a few cave temples.

Evenings are equally quiet in both, and neither has a club worth seeking out. The difference is in the setting. In Chiang Rai you go to the short strip of small bars by the clock tower, with reggae or acoustic sets, or linger at the beer tables by the night bazaar stage. In Kanchanaburi you drink on the riverside backpacker road, with pool tables and cover bands, and weekends get noisier when Thai groups hire karaoke rafts that drift down the river.

Both are good bases for the outdoors, but the landscapes differ. Chiang Rai is hill country: tea terraces on Doi Mae Salong, the gardens of Doi Tung, the sea of cloud at sunrise from Phu Chi Fa and the wide Mekong at the Golden Triangle. Its weak point is the smoke haze from burning fields in late winter and spring.

Kanchanaburi has lower limestone jungle along the Burmese border, with more water to enjoy. The trail climbs past Erawan's seven tiers of falls, and there are caves at Sai Yok and Lawa and kayaking on the dam reservoirs. Here the waterfalls run thin late in the dry season, so both are at their best just after the rains.

There are about as many outings from each, and the difference is what they show you. From Chiang Rai you head to the borders: the ruined chedis of Chiang Saen on the Mekong, the Golden Triangle viewpoint and its opium museum, the market at Mae Sai and the Yunnanese tea village of Doi Mae Salong.

Kanchanaburi's best outing is the old railway itself, running along the cliffs to Nam Tok and on to the cutting at Hellfire Pass. It also faces east towards the centre of the country, with the great chedi at Nakhon Pathom, the canal markets of Damnoen Saduak and Amphawa, and even Bangkok for a long day.

Both towns are friendly to children but have little built for them, and in both you spend a lot of time in vehicles. Kanchanaburi has more hands-on fun: splashing in the Erawan pools, sleeping in a raft house and riding the slow train, although the war cemeteries mean little to young children. In Chiang Rai the main outing is the open space of Singha Park with its tea fields and lakes, and the colourful temples hold children's attention for a morning. Avoid the smoky spring season there.

Getting around is about equally awkward, for different reasons. Chiang Rai's centre around the clock tower is small enough to walk, and a local bus runs to the White Temple, but everything else needs a tuk-tuk, a driver or a scooter. Kanchanaburi is spread out along the river for several kilometres, so a bicycle is the easiest way to get about. In return, its slow train up the Death Railway is a sight in itself as well as a way to travel.

Chiang Rai is the better place to shop, even though it is mostly markets. The nightly bazaar and the longer Saturday walking street on Thanalai Road sell hill-tribe textiles, silver and carved wood, and Doi Mae Salong oolong and local coffee are worth packing.

Kanchanaburi has only the night market, the souvenir stalls by the bridge and a few gem shops selling the province's blue sapphires. Those shops are only worth trying if you know how to judge stones.

Both are among the cheapest stops in Thailand, with guesthouses, market meals and massages costing very little. The spending adds up in different places. In Chiang Rai the big cost is reaching sights that lie far out in the hills, which usually means a driver, a hire car or a tour. In Kanchanaburi the local train and buses cost almost nothing, but foreigner entry fees at the national parks and the comfortable resorts upriver add up.

Neither town has theatre or a concert season, but Chiang Rai offers a little more on an ordinary evening. Lanna dance and folk music play on the night bazaar stage, and khantoke dinners pair northern dishes with traditional dancing. Kanchanaburi's live music is cover bands in the riverside bars. Its one real show is River Kwai Bridge Week, a sound-and-light restaging of the wartime bombing of the bridge, held around late November and early December.

Chiang Rai suits a wellness trip with a little more structure. You can soak in the simple hot spring pools at Pong Phrabat north of town or at Mae Kachan on the road south, and join a meditation or yoga retreat in the surrounding countryside. It is best avoided in the smoky late-winter and spring months.

In Kanchanaburi, relaxing means doing very little on the upper River Kwai, in a hammock on a raft house or riverside resort with jungle on the far bank. Its only hot springs, at Hin Dat, are two hours away. In both towns a cheap Thai massage is never far off.