Istanbul or Marmaris?

Marmaris is a place you go to swim. The long sand-and-shingle strip along the promenade faces a sheltered bay with calm, clear water, and the boats that leave each day stop at coves where the water is clearer still. Sedir Island and the pebble bays of Bozburun add variety for anyone willing to travel.

Istanbul sits on the water but you hardly swim there. The sea near the centre is not for bathing, and the sandy Black Sea strands at Kilyos and Sile are an hour away and have strong undertow. The Princes' Islands give a pleasant half day in a pebbly cove, nothing more.

This is where Istanbul pulls far ahead. Cooking from every corner of Turkey meets in one city, from Black Sea anchovies to south-eastern lahmacun and Ottoman palace dishes, and there are meyhane nights in Beyoglu and Kumkapi and long grazing walks through Kadikoy's market streets.

Marmaris eats more simply. The seafront mostly serves resort menus, and the good meals are found in lokantas, pide houses and harbour fish restaurants a street or two back. The weekly market and the local pine honey are the real food pleasures here.

Istanbul has some of the greatest sights in the Mediterranean world: Hagia Sophia, Topkapi, the Basilica Cistern and the Chora mosaics on one peninsula, plus Ottoman palaces and fortresses along the Bosphorus. A week does not exhaust it.

In Marmaris, culture means the small castle above the harbour, its modest museum and an hour among the whitewashed lanes of the old quarter. History lovers based there spend their time on excursions, not in town.

Istanbul gives more choice and keeps it going all year. You can have rooftop drinks over the Golden Horn, late meyhanes off Istiklal that end in singing, polished cocktail bars in Karakoy, cheap craft-beer streets in Kadikoy and, in summer, Bosphorus clubs at Ortakoy that run until dawn.

Marmaris has one loud kind of night out. Bar Street fills after midnight with lasers, foam parties and a young, mostly British crowd, while the marina offers calmer drinks. Most of it shuts between November and April.

Marmaris is surrounded by landscape. Pine forest comes down to the bay, and the Bozburun and Datca peninsulas are a lightly built coast of inlets and islands, one of Turkey's great sailing grounds. The Carian Trail, diving and sea kayaking make it easy to get out into it.

Istanbul's nature is gentler and more urban: the wooded Bosphorus seen from a ferry, April tulips in Emirgan, Belgrad Forest trails and cycling on the Princes' Islands. There are no mountains nearby, and leaving the city takes a long time.

Marmaris has the stronger outings. Rhodes's walled medieval town is an hour away by ferry, Dalyan has its river boats beneath Lycian rock tombs, and the ruins of Knidos lie at the far tip of the Datca peninsula. Several of these need a tour or a hire car.

From Istanbul the easy escapes go by water: the Princes' Islands and an upper-Bosphorus cruise to Anadolu Kavagi. Bursa is the best town to visit, but Edirne and Iznik make long days, and Gallipoli and Troy need a night away.

Marmaris is easier with children, as long as the plan is beach and pool. The shallow edges of the bay, hotel kids' clubs, a large water park and boat trips with swimming stops keep them busy, and families stay in Icmeler or Armutalan, away from Bar Street.

Istanbul has more to see, with ferries, the ships and submarine at the Rahmi M. Koç Museum, Miniaturk and aquariums. But the crowds, steep cobbled hills and long transfers tire small legs and defeat pushchairs. Marmaris has its own catch: little beyond the water, and midday heat in midsummer.

Istanbul's network does more for a visitor. One card covers the tram through the old city, the metro, the Marmaray tunnel and the ferries between continents, though rush-hour crowds and slow taxis are part of the deal.

Marmaris is simple only inside the bay, with a flat seafront promenade, frequent dolmus minibuses and water taxis to Icmeler and Turunc. The peninsula villages, Datca and Dalyan are reached on winding roads with few buses, so many visitors hire a car for a few days.

Istanbul is one of the great shopping cities. The Grand Bazaar's hans and covered streets sell carpets, lamps and ceramics, Nisantasi has the designer labels, Cukurcuma the antiques and Kadikoy the flea markets.

Marmaris has a single covered bazaar heavy on leather and copy designer goods. The things worth taking home are local: pine honey, natural sponges, olive oil soap and peshtemal towels.

Overall costs come out about even, but you spend the money on different things. In Istanbul transport, tea and street food cost very little, while hotels in Sultanahmet and Galata, the heavily taxed alcohol and the entry fees at the big monuments add up quickly.

In Marmaris the savings come from keenly priced all-inclusive and package hotels and cheap lokanta meals. The extras are boat trips, seafront dining and Bar Street, and rooms cost less in spring and autumn.

Istanbul offers real evenings out. The state opera and ballet perform at the Ataturk Cultural Centre, summer festivals put jazz and concerts into historic courtyards and churches, and Sema ceremonies take place in old dervish lodges. Small venues in Beyoglu and Kadikoy play Anatolian folk and rock.

Marmaris has hotel shows, staged Turkish nights and the odd summer concert in its amphitheatre, and nothing you would plan a trip around.

Istanbul's historic hammams are the stronger draw. In bathhouses such as Cemberlitas and Kilic Ali Pasa, Sinan's marble domes and star-pierced skylights turn a scrub into one of the highlights of the visit. Marmaris has hammams too, but they are modern ones run for tourists.

Marmaris is better if you simply want peace and quiet. Istanbul is noisy and crowded, and its calm is limited to a bath or a Bosphorus tea terrace, while Turunc, Selimiye and Bozburun are slow places, and the Dalyan mud baths make a lazy half day.