Hong Kong or Shenzhen?

On the beach the two are evenly matched, with equally warm summer water, but getting to the sand is very different. Hong Kong's beaches are close: Repulse Bay and Deep Water Bay are a short bus ride from Central, Shek O feels like a village outing, and most have lifeguards and shark nets in season. That makes a swim easy to fit into a city afternoon.

In Shenzhen every beach is out on the Dapeng peninsula, an hour or more from Futian. Xichong's wide curve of sand facing the open sea is the most attractive of either city's beaches, but Dameisha and Xiaomeisha get very crowded on summer weekends, so plan a full day for the trip.

Hong Kong is one of the great food cities, and Shenzhen does not match it. Hong Kong has Cantonese cooking at its most refined, a diner culture of milk tea and pineapple buns that exists nowhere else, and whole neighbourhoods such as Sham Shui Po and Sheung Wan where eating shapes the streets.

Shenzhen's strength is range rather than depth. Migrants from across China cook Chaoshan beef hotpot, Hakka salt-baked chicken and fiery Hunan dishes, which is more regional variety than you will easily find in Hong Kong. However, most of these meals are eaten in malls and office districts, and menus behind QR codes make a translation app essential.

Hong Kong gives you far more to see. The harbour skyline from Tsim Sha Tsui, Man Mo Temple's incense, the old Central Police Station, and the M+ and Palace Museum pair in West Kowloon add up to several full days of sightseeing.

Shenzhen's landmarks are mostly modern, from the Ping An tower to the converted factories of OCT Loft, with Dafen's painting workshops as its oddest sight. Its older pieces, Nantou's Ming-era lanes and the Hakka walled villages of Longgang, are worth the trip but are scattered and few. Anyone after history will find more in Hong Kong or in nearby Guangzhou.

Hong Kong's nights out are better, mainly because they spill onto the street. Crowds drink on Lan Kwai Fong's steep lanes, Soho and Sheung Wan have serious cocktail bars, and Wan Chai keeps going into the early hours. Kowloon adds beer at seafood stalls under neon.

Shenzhen does better where Hong Kong is weak, with large clubs, bottle service and big-room DJs around Coco Park. Shekou's terraces and craft beer suit a quieter evening. Otherwise the venues are spread out and tucked into towers, and a private karaoke room is the most local night out.

Hong Kong has the wilder and more striking outdoors. Country parks cover much of the territory, and the Dragon's Back ridge, sunrise on Lantau Peak and Sai Kung's volcanic columns and sea caves are all an easy public transport ride from the towers.

Shenzhen's green spaces are pleasant but gentler. Wutong Mountain, at just under 950m, is a proper climb with views across to Hong Kong, and the Dapeng coastal trail between rocky coves is a good day out. The rest is mostly park greenways and the flat Shenzhen Bay path past the mangroves, better for cycling and birdwatching than for hard hiking.

Shenzhen is the better base for day trips, because it sits closer to everything. Fast trains reach Hong Kong's West Kowloon in under half an hour and Guangzhou in about the same time, and Foshan's ancestral temple is just beyond, so three very different cities are within easy reach.

Hong Kong reaches Macau and Guangzhou easily too, but its best short outings are its own outlying islands: Cheung Chau's harbour, Lamma's car-free villages and Tai O's stilt houses. Whichever city you stay in, crossing the border means checking your passport and visa rules, and from Shenzhen you also need the right arrangements to get back into the mainland.

Both cities are safe, clean and easy with children, and the difference is in the kind of day out. Hong Kong has Disneyland and Ocean Park's pandas and aquarium, and simple pleasures like the Peak Tram and the Star Ferry, but weekend crowds and very small hotel rooms make it harder work.

Shenzhen gives families more space for less money, with the Happy Valley, Window of the World and Splendid China cluster in Nanshan and a drive-through safari park. The drawbacks are long journeys between attractions and little English away from the main parks.

Hong Kong is easier to get around. The sights are close together, the MTR, trams and Star Ferry all run on one stored-value card, and the Mid-Levels escalator and covered walkways help on the hills.

Shenzhen's metro is good, with bilingual signs and links to the border and the theme parks, but the city stretches some 80km. Going from Shekou to the beaches takes most of a morning, and multilane roads make walking between districts dull. Set up the mobile payment apps before you arrive, because most things are paid for that way.

Hong Kong is the stronger shopping city overall. Canton Road and Central are lined with luxury flagships, there is no sales tax, and Mong Kok's flower and goldfish markets or the curio shops of Cat Street work as sightseeing too.

Shenzhen has one thing Hong Kong cannot match: Huaqiangbei, floor after floor of stalls selling phones, drones and electronic components. Luohu's tailors and Dafen's hand-painted canvases are fun as well. Beyond those, its shopping is mostly polished malls, with little luxury on the street and few crafts to take home.

Shenzhen is much cheaper, and the difference shows most in where you sleep. A comfortable modern hotel there costs far less than Hong Kong's small, expensive rooms, and an ordinary hotpot dinner or dim sum lunch is cheap.

Hong Kong can be managed carefully if you eat in noodle shops and neighbourhood teahouses, ride the almost-free Star Ferry and spend your days on the free hiking trails. Harbour-view dinners and Central cocktails, however, cost as much as in any Western capital. Some travellers stay in Shenzhen and visit Hong Kong for the day for exactly this reason.

Hong Kong offers more for a visitor who wants a night of performance. The Philharmonic plays on the Tsim Sha Tsui waterfront, and Cantonese opera, with its painted faces and loud percussion, is staged at the Xiqu Centre and at village bamboo theatres. The annual Arts Festival brings in international companies.

Shenzhen has fine modern halls in Futian, but its programme is mostly touring shows and Mandarin theatre. Its most distinctive offer is the Chinese indie and rock bands in small live venues around OCT Loft.

Shenzhen is the place to unwind, thanks to its bathhouses. These huge complexes run through the night with hot and cold pools, saunas, sleeping halls and massage floors, and people cross the border from Hong Kong just to spend an evening in one. Hot-spring resorts in the hills of Huizhou add more.

Hong Kong matches it on foot reflexology parlours and has some of Asia's most polished hotel spas, but it has no bathing tradition and its streets are anything but calm. Real quiet there means a trip to Chi Lin Nunnery's gardens or an afternoon on Lamma.