Ayutthaya or Bangkok?

Neither city is a place to swim in the sea, and Ayutthaya, far inland on the central plain, is even further from it. Its rivers are working waterways, so the hotel pool is the only option.

Bangkok's own coast is mudflat and mangrove, so it does little better, but its hotels are known for their rooftop pools, and Bang Saen or Pattaya make a long day out. From either city, beach days belong on the islands or at Hua Hin.

Ayutthaya eats well for a provincial town. It has boat noodles by the bowlful, giant river prawns grilled by the water and roti sai mai sold near the old Muslim quarter, while the night markets cover the basics. There is almost nothing international.

Bangkok is in another league. Boat noodles are one dish among hundreds there. Yaowarat after dark and the Talat Noi riverside are made for grazing, and Or Tor Kor shows off the country's produce. Ambitious regional Thai kitchens, strong Japanese and Chinese cooking and a serious cocktail culture sit on top of all the street food.

Both are first-rate for Thai history, but one shows it in ruin and the other still in use. Ayutthaya is the fallen capital: brick prangs, headless Buddhas, the stone head in the tree roots at Wat Mahathat and Wat Chaiwatthanaram against the sunset, spread across an island and its banks.

Bangkok is the capital that replaced it, with the gilded spires and mirrored tiles of the Grand Palace, the Reclining Buddha at Wat Pho and temples where worship carries on around you. The National Museum, Jim Thompson House and Chinatown widen the range, whereas Ayutthaya goes deeper into a single theme on a remarkable scale.

Ayutthaya goes to bed early. There are a few backpacker bars and some riverside terraces facing the floodlit ruins, and most visitors are in well before midnight. Bangkok has one of Asia's best-known nights out, from the cocktail bars of Thonglor and Ekkamai to the street party on Khao San Road, Silom's gay scene and the rooftop bars above the river, with food stalls still serving after closing.

Neither city is a trip for landscape, and in both the outdoors is flat and hot. Ayutthaya's version is rural: rice fields and canals, storks and egrets over the paddies, and a long-tail boat round the island at dusk.

Bangkok's is green space inside a huge city, such as the monitor lizards of Lumphini Park and the raised cycle paths of Bang Krachao through palms and orchards. Khao Yai's forests are a couple of hours or more from either, and from Bangkok the river country of Kanchanaburi is another option.

Each city is the other's best day out. From Ayutthaya, Bangkok and the Bang Pa-In summer palace come first, and Lopburi's Khmer temples and macaques are a good third, but after that the central plain has little more to offer.

Bangkok has more within reach. Besides Ayutthaya itself, there are the floating and railway markets of the canal country, the great stupa at Nakhon Pathom, and the Death Railway bridge and war cemeteries at Kanchanaburi for a long day.

Ayutthaya holds children's attention for a morning, helped by the tree-root Buddha head and the open temple grounds. But climbing is not allowed on many of the monuments, shade is scarce and nothing is designed for young visitors.

Bangkok has Sea Life Ocean World beneath Siam Paragon, Safari World, Dream World, KidZania and air-conditioned mall play areas for hot afternoons, and children are made a fuss of everywhere. Its heat, traffic and crowded pavements are tiring for small children, but there is far more to fill a family's days.

In Ayutthaya the bicycle does the work. The island is flat and a few kilometres across, with tuk-tuks for half-day circuits and small ferries to the temples across the water, but there is no useful bus or rail network. Bangkok has the Skytrain, the MRT and the Chao Phraya Express boats linking the main districts and the riverside sights, with ride-hailing for the gaps.

The catch in Bangkok is its size: road traffic crawls and walking between stations is hot and awkward. Ayutthaya's distances are short, so it matters less there that the only ways around are slow.

Ayutthaya offers little beyond night-market clothes, amulets and souvenir stands, with the Bang Sai crafts centre downstream as its one real speciality. Bangkok is one of Asia's great places to shop: the chain of malls around Siam and Ratchaprasong, Pratunam's wholesale clothing, Chinatown's gold shops and, above all, Chatuchak Weekend Market. Thai silk, celadon and benjarong porcelain are easy to find in the capital.

Both are very cheap by international standards, and Ayutthaya makes money go a little further. Riverside guesthouses and hotels with pools cost little even by Thai standards, and bicycle hire costs next to nothing. The main outlay is the separate entrance fee at each major ruin.

Bangkok is nearly as easy on a budget for street food, transport and hotels, but it gives you more ways to spend. Imported drinks are heavily taxed, rooftop bars and international restaurants charge global prices, and rooms in Sukhumvit or on the river cost more.

Ayutthaya has almost nothing to see on an ordinary evening. The exception is the annual World Heritage fair, with light-and-sound shows among the ruins. Bangkok stages khon masked dance drama at the Sala Chalermkrung Royal Theatre and the National Theatre, as well as classical music and dance and a symphony orchestra at the Thailand Cultural Centre. It also has small jazz and blues bars, and Muay Thai fights at Rajadamnern and Lumpinee with their ritual music.

You can get a Thai massage easily in both, but Bangkok takes it much further. Wat Pho's massage school still treats clients in the temple grounds, parlours stay open late on every street and the grand hotels run some of Asia's most refined spas. Ayutthaya has simple shophouse parlours and few upmarket spas.

What Ayutthaya has instead is quiet. Once the tour buses leave, evenings by the river become slow and peaceful in a way that Bangkok's noise and traffic rarely allow.