Seoul or Ulaanbaatar?

Neither city is a place to swim, but Seoul at least has sand within reach. The Yellow Sea beaches at Eurwangni and on Muuido are an hour or more away, with big tides and murky water. In summer there are also the outdoor pools in the Han River parks.

Ulaanbaatar is completely landlocked, and the cold shallows of the Tuul are only good for paddling. If you want a real beach, go to Busan or Korea's east coast.

Food is one of the strongest reasons to choose Seoul. Meals mean barbecue cooked at the table, stews in stone pots, cold noodles and fried chicken, always with a spread of side dishes. Gwangjang Market and the tented street stalls stay busy late, and there is fine dining and a café culture on top.

Ulaanbaatar's food is filling fuel for the cold: buuz dumplings, khuushuur and salty milk tea. It is heavy on mutton and hard for vegetarians. Its best variety comes from Korean barbecue places, and Seoul has the original in much greater range.

Seoul's heritage is deeper and broader. It has five Joseon palaces, the UNESCO-listed Changdeokgung and Jongmyo, the hanok lanes of Bukchon and the National Museum of Korea. Together they fill several days, though the sights come in clusters among modern towers.

Ulaanbaatar's sights are fewer but unlike anything in Seoul, and they grow out of its Buddhist past. Monks chant at Gandan, and you can visit the Choijin Lama Temple, the Bogd Khan's Winter Palace and the gilded bronzes in the Zanabazar museum. Two or three days covers them.

A night out in Seoul moves in rounds, from barbecue and soju to fried chicken and beer to a small pub. Hongdae's clubs and buskers, Itaewon's cocktail bars and Gangnam's dressed-up clubs are still full at 3am. Ulaanbaatar has fun to offer around Sukhbaatar Square and Seoul Street, with pubs, karaoke and a few clubs, but the scene is small. It is liveliest in summer and quiet through the frozen winter.

Both cities have real outdoors on the doorstep, but of very different kinds. In Seoul hiking is a city habit. The subway takes you to Bukhansan's granite ridges, Inwangsan gives a short climb above the palaces, and cycle paths run along the Han.

Ulaanbaatar has wilder, emptier country. There is larch forest on Bogd Khan Uul at the edge of town, horse riding in Terelj and wild takhi horses at Hustai. It is a summer-only option, and traffic on the way out takes time.

Seoul has far more for extra days. Suwon's walled fortress is about an hour away, and there are also Namhansanseong, tours to the DMZ and Jeonju's hanok quarter by KTX. Trains make most of these easy without a guide.

From Ulaanbaatar the choices are few, and most need a driver. You can see the giant steel Chinggis Khaan at Tsonjin Boldog, the ruined Manzushir Monastery or a herding family. Kharkhorin, the old imperial capital, is too far for a day and needs a night away.

Seoul is well set up for children. Lotte World is in the city and Everland's safari is an hour south, and there are big aquariums, good science centres, safe streets and lifts in the stations.

In Ulaanbaatar, children enjoy the countryside most: nights in a ger, gentle horses and marmots, plus the real Gobi fossils at the dinosaur museum. In the city itself, hard road crossings, broken pavements and smoky winter air make it tiring with children.

Seoul's subway is clean, punctual and signed in English. It reaches the palaces, Gangnam and the hiking trailheads alike. The one drawback is the city's size, so it pays to stay near the areas you will use most.

Ulaanbaatar has no metro or tram, and its buses are labelled in Cyrillic and stuck in heavy traffic. You can walk the small centre around Sukhbaatar Square. Beyond it you need taxis, and a hired driver for the countryside.

Seoul is worth a trip for shopping alone. It has Korean skincare in Myeongdong, fashion malls in Dongdaemun that trade all night, designer stores in Seongsu and Garosu-gil, and crafts in Insadong. Ulaanbaatar does one thing well, cashmere, sold in factory outlets and the State Department Store, along with felt goods, deel robes and horse-head fiddles. Go to Seoul for variety and trends, and to Ulaanbaatar for a suitcase of sweaters.

Ulaanbaatar is the cheaper city day to day. Canteen meals, taxis and museum entry cost little, though central hotels and Western restaurants cost about what they would in Southern Europe. The big expense is the countryside, where a driver and vehicle can cost more than everything else.

Seoul is mid-priced for a capital. Transport and casual Korean meals are good value, but hotels, barbecue dinners and smart cafés push the total up. A stay in the city costs less in Ulaanbaatar, but a trip built around the steppe may not.

Seoul gives a visitor more to choose from. The Seoul Arts Center and Sejong Center have orchestras and opera, the National Gugak Center stages court music, and Hongdae has indie clubs. Most of Daehangno's theatre, though, is in Korean.

Ulaanbaatar has one show every visitor should see: a summer evening of throat singing, horse-head fiddle and contortionists. Tickets for the ballet at the pink State Opera theatre are also easy to get.

In Seoul, relaxing is part of everyday life thanks to the jjimjilbang. These bathhouses are open around the clock, with hot pools, body scrubs and heated rooms of clay and salt, and the city adds skincare spas and temple stays. Ulaanbaatar has little more than hotel spas and a few saunas. Rest there means leaving town for a ger camp in Terelj, with silence and a wood stove.