Halkidiki or Zakynthos?

The two are evenly matched for swimming, but the beaches feel different. Halkidiki has far more coastline: long sand and fine pebble backed by pine forest, with sunbeds and beach bars on Kassandra and granite coves at Kavourotrypes and Karydi on Sithonia. With three peninsulas to choose from, it is easy to find a quieter stretch.

Zakynthos packs more variety into a small island. It has the sandy curve of Laganas Bay, protected turtle beaches at Gerakas and Dafni that stay undeveloped, rock-ledge swimming on the west coast and boat-only coves. Its most famous view, the wreck at Navagio, is something to look at from above or from a boat rather than a beach to spend the day on.

Eating is much the same in both: honest seaside tavernas with grilled fish, salads and slow-cooked dishes, at their best in villages away from the main resorts. Halkidiki's products are its big green olives, pine honey and the wines from Athos and the slopes above Neos Marmaras, and Thessaloniki is close enough for a day of serious eating.

Zakynthos has more dishes of its own. Look for garlicky skordostoumbi, ladotyri cheese kept in olive oil, mantolato nougat and Verdea white wine, best in the villages around Keri. In Laganas and Tsilivi the menus turn international.

Halkidiki has more to see, and its centrepiece is Mount Athos. Most visitors see the monasteries from a boat out of Ouranoupoli, and only men with a permit can go ashore. Olynthos, Stagira, the Petralona cave and the stone village of Afytos fill a few more half-days.

On Zakynthos, the 1953 earthquake took most of the Venetian capital. What remains is a short circuit of the Byzantine Museum's Ionian icons, the Solomos museum, the church of Agios Dionysios, the castle on Bochali hill and the monastery of Anafonitria.

Zakynthos has the bigger and rowdier summer scene, almost all of it on the Laganas strip. Bars and clubs there run until dawn, with foam parties and promoters, mostly aimed at young British groups. Away from Laganas the island goes quiet, and anyone who wants calm evenings should stay well clear of it.

Halkidiki's nights are smaller and more Greek. There are open-air clubs at Kallithea and cocktail bars in Pefkohori and Hanioti, busiest when young people drive in from Thessaloniki at weekends. Sithonia is for long dinners by the water.

Zakynthos has more for the active nature lover. Laganas Bay is a national marine park where boats find nesting loggerhead turtles, and the cliffs at Keri and Navagio are dramatic viewpoints. You can kayak or dive below them, and walk or cycle the olive hills towards Mount Vrachionas.

Halkidiki's best scenery is where pine forest meets the sea on Sithonia, around Mount Itamos and the islets off its coast. Activities there centre on sailing to the Diaporos lagoon and kayaking the coves. The paths between the Athos monasteries are the one serious hike, open only to men with a permit.

This is where Halkidiki pulls clearly ahead. Being on the mainland puts Thessaloniki within easy reach, and the royal tombs at Vergina, Pella, Kavala and ancient Amphipolis all make full days out. Ammouliani is a short ferry ride from the Athos side.

From Zakynthos, every trip off the island starts with a ferry. That still allows a summer day on southern Kefalonia or a long day to ancient Olympia via Kyllini, but most visitors settle for a tour of the island's own villages and viewpoints.

Both work well for a beach vacation with young children. Halkidiki's advantage is sand and calm water that stays shallow a long way out, at Gerakini, Psakoudia and much of Kassandra, plus large family resorts. On the other hand, it has nothing like a theme park, and the drives between peninsulas are long.

Zakynthos is small, so journeys stay short. It also has an inland water park and turtle-spotting boats that children love. Stay at Tsilivi or Alykes rather than near Laganas, and remember that several famous beaches can only be reached by steep paths or by boat.

You will want a car in either place, and neither has buses you could plan a stay around. In Halkidiki the problem is distance. Each peninsula is a long finger of land, so crossing from Kassandra to the Athos side means driving back up to the top of one and down the next, and southern Sithonia is close to two hours from the airport.

Zakynthos is only about 40km long, but the roads in the west and north are narrow and winding. Many beaches and caves are reached by boat, and taxis are easy to find in the resorts.

Neither is a place to shop. The resort strips in both mostly sell beachwear and souvenirs, and the best things to take home are honey, olive oil and wine. Halkidiki adds the icons and incense sold in Ouranoupoli, and Thessaloniki is within reach for real shopping.

Zakynthos has mantolato nougat, village lace and weaving from around Volimes, and the local shops on Alexandrou Roma street in Zakynthos Town.

Costs are much the same, with moderate prices by Mediterranean standards in both, and in both June and September are cheaper than August. In Halkidiki, the many Greek and Balkan families who drive in keep plenty of simple rooms and village tavernas in business, and costs rise at the big Kassandra resorts.

Zakynthos is built around package tourism, which keeps resort rooms moderately priced. Boat trips and car hire add up over a week there.

Neither offers much, but what there is differs in kind. Halkidiki has organised summer seasons: concerts and theatre at the open-air amphitheatre in Siviri for the Kassandra Festival, and jazz and classical evenings at Sani. Thessaloniki is close for anything more.

Zakynthos has a living folk tradition instead. Small groups sing kantades and arekia serenades in the tavernas, the town's old philharmonic band plays at religious feasts, and villagers perform omilies street theatre at carnival.

Halkidiki is the better choice for rest and restoration. It has real thermal bathing in the warm mineral pools at Agia Paraskevi above the sea, serious spas at its large resorts, and long, calm stretches of coast on Sithonia and towards Ouranoupoli.

Zakynthos has spas in its larger hotels and cool sulphur springs bubbling into the sea at Xigia. Its quiet comes mainly from where you stay: the hill villages around Keri and Agios Leon, or the Vasilikos peninsula, far from Laganas.