Istanbul or Varna?

This is Varna's clearest advantage. A lifeguarded city beach runs right below the Sea Garden, and St Konstantin and Elena and Golden Sands add wide sand with a gentle slope and usually small waves. You can go for a swim between other plans without making a day of it.

Istanbul's centre sits on the water, but it is not a place to bathe. Swimming means a trip of about an hour to Kilyos or Sile, where currents and undertow keep you to the lifeguarded stretches, or a ferry to the small pebbly coves of the Princes' Islands.

In Istanbul, food is a reason to travel in itself. Dishes come from every Turkish region, there are lokanta stews at lunch, fish sandwiches by the Galata Bridge and long meyhane evenings in Beyoglu and Kumkapi, and you could eat something different at every meal for a week.

Varna is simpler and more seasonal: fried sprats, farmed mussels, grilled meats and shopska salad with a glass of Black Sea white. It is honest and satisfying but repeats itself quickly, and many of the seafront kitchens close after summer.

The gap here is wide. Istanbul's historic peninsula alone holds Hagia Sophia, the Blue Mosque, Topkapi and the Basilica Cistern within walking distance of each other. Beyond them lie Sinan's mosques, the Chora mosaics, the Theodosian land walls and the Bosphorus palaces.

Varna has one sight of world rank, the six-thousand-year-old gold from the Necropolis, along with the Roman Thermae and the Aladzha monastery carved into the cliff. It makes a rewarding day or two of sightseeing but will not carry a whole trip.

Istanbul's nights are bigger and go on all year. There are rooftop bars and singing meyhanes off Istiklal Avenue, polished cocktail bars in Karakoy and Cihangir, cheaper bar streets in Kadikoy and Moda, and clubs on the Bosphorus in summer. The heavy tax on alcohol makes it an expensive night, though.

In Varna, going out is a summer affair at the beach clubs below the Sea Garden, with a young crowd and late hours, and louder package-style partying at Golden Sands. Out of season it shrinks to pubs and cocktail bars in the pedestrian centre.

Neither city has mountains nearby, and both offer gentle outdoor days rather than serious hiking, but the settings differ. Istanbul's outdoors means the wooded Bosphorus seen from ferries and shore paths, tulip parks in April, the trails of Belgrad Forest and cycling on the car-free Princes' Islands.

Varna's is more coastal and more unusual: the shaded Sea Garden, the stone columns of Pobiti Kamani, the flooded forest along the Kamchia and the red cliffs of Cape Kaliakra, where dolphins are often seen offshore. Some of it starts right at the edge of town, while getting out of Istanbul takes time.

The two are close here, and the difference is in how you travel. From Istanbul the best outings are by boat, to the Princes' Islands or up the Bosphorus to Anadolu Kavagi, with Bursa as the strongest town trip. Edirne and Iznik make long days.

Varna's outings go by road, along the coast and inland, and most are an hour or so away: Nessebar's medieval churches, the queen's palace and gardens at Balchik, and the Madara Rider with the old capitals of Pliska and Preslav. The choice is a little wider and closer to hand, but a hire car or a tour helps.

Varna is easier with children. The zoo, aquarium, planetarium and playgrounds are grouped in the Sea Garden just above a lifeguarded beach, the seafront is flat enough for a pushchair, and water parks are a short ride north.

Istanbul makes a bigger fuss of children than almost anywhere, and ferry rides and the Rahmi M. Koç Museum always go down well. But the crowds, steep cobbled hills and long transfers soon wear out small legs.

Istanbul has the fuller transport network. One card covers the metro, the tram, Marmaray, the funiculars and the ferries, and crossing between continents by boat is a highlight in itself. Expect a crush on the T1 at rush hour and slow taxis.

Central Varna is small and flat, so you can walk from the cathedral to the beach in a quarter of an hour. Beyond the centre you depend on buses with Cyrillic signs, cheap taxis, or a hire car for the day trips.

Istanbul is worth visiting for its shopping alone. There are carpets, lamps and leather in the Grand Bazaar, spices in the Spice Bazaar, designer labels in Nisantasi, antiques in Cukurcuma and flea markets in Kadikoy. Leave room in your luggage.

Varna offers high-street fashion along Knyaz Boris I and a few malls. Rose oil cosmetics, embroidered linen and local wine are the souvenirs worth taking home.

Varna makes a budget go further. Tavern meals, wine, taxis and museum tickets cost well below Western European levels, and only July and August push room rates up sharply, mostly at the resorts.

Istanbul is cheap for transport, simit and lokanta lunches, but the tourist districts of Sultanahmet and Galata come close to Southern European prices. Drinks are heavily taxed, and the major monuments charge foreign visitors high entry fees.

Istanbul has more to choose from on any given night. The state opera and ballet perform at the Ataturk Cultural Centre, concert halls host touring names and the summer festivals bring jazz to historic courtyards. Sema ceremonies and live folk and rock in Beyoglu and Kadikoy add to it.

Varna has a fine opera house on its main square and the long-running Varna Summer festival, which is a lot for a city of its size. Outside summer, though, the programme is modest and mostly in Bulgarian.

Istanbul comes out ahead because its bathing culture is public and still part of everyday life. You can walk into a sixteenth-century hammam in the old city, or a neighbourhood bath where local people go, and leave scrubbed and slowed down without booking a hotel. Varna's warm springs fed Roman baths too, but there is no bathhouse tradition to step into. Mineral pools and mud treatments mostly mean a spa hotel at St Konstantin and Elena or Golden Sands, outside the centre.

When it comes to calm, the balance tips the other way. Beyond the bath door, Istanbul stays loud and crowded, so its quiet comes in pockets, such as a ferry crossing or a tea on a Bosphorus terrace. Outside the beach-club weeks of high summer, Varna is quiet enough that the Sea Garden and the bay give you an unhurried day without having to look for it.