Halkidiki or Kefalonia?

For beaches the two are equally strong, and the difference is in the kind of shore. Halkidiki's three peninsulas have long runs of pale sand and fine pebble backed by pines. Kassandra has the organised beaches with sunbeds, and Sithonia has granite coves.

Kefalonia's beaches are more dramatic and spread across different coasts. There is the white pebble curve of Myrtos below its cliffs, Petani on Paliki, and gentler sand at Skala, Lourdas and Xi. On the island you drive between coasts to find the beach you want, while in Halkidiki one peninsula can keep you busy for a week.

Both eat at the seaside taverna, and neither suits someone looking for fine dining. Kefalonia has more dishes of its own: meat pie, aliada with salt cod, mandoles, and Robola wine tasted at the Omala valley wineries.

Halkidiki relies more on grilled fish, mussels and its large green olives, which are best in Nikiti, Toroni and the hill villages. It also has something the island lacks, as Thessaloniki's restaurants are close enough for a day trip.

Neither is a culture destination, but Halkidiki has the one sight of real weight. Mount Athos has monasteries perched on cliffs, which most visitors see from a boat out of Ouranoupoli and which men with a permit can visit. Olynthos, ancient Stagira and the Petralona cave fill a few more half-days.

The 1953 earthquake destroyed most of Kefalonia's old buildings, so what remains is scattered: Venetian Fiskardo, the fortress at Assos, the Castle of Agios Georgios and the Mycenaean tomb at Tzanata. They make pleasant outings, but there is less of it.

Halkidiki is the clear choice for going out, though only on Kassandra and only in summer. Kallithea has open-air clubs, and Pefkohori and Hanioti have bar strips that fill at weekends with young people driving in from Thessaloniki.

Evenings on Kefalonia are slower. They centre on a long dinner and a drink in Argostoli's main square, along the bar strip at Lassi or by the harbour at Skala and Fiskardo. There are few places to dance, and outside high summer most bars are quiet before midnight.

Kefalonia has the grander landscape. Mount Ainos rises to about 1,628m inside a national park of Greek fir, the west coast drops in white cliffs, and under the island lie the Melissani lake cave and the Drogarati chamber. Loggerhead turtles feed in Argostoli harbour.

Halkidiki is gentler, with pine forest running down to clear water, at its best on Sithonia's granite headlands and the slopes of Mount Itamos. It suits kayaking and boat trips to Diaporos better than walking, as its one serious hike, between the Athos monasteries, is open only to men with a permit.

Halkidiki has more to choose from, mainly because Thessaloniki, with its Byzantine churches and good food, is about an hour or so away by road. Vergina and Pella, Kavala and Amphipolis are also possible in a day, and Ammouliani is a short ferry ride.

Kefalonia's best day out is a very good one: Ithaca, by ferry from Sami. Summer boats also reach Zakynthos and Lefkada, but most crossings run only in season, and after those the choice soon runs out.

Halkidiki is the easier choice for families. The sandy water stays shallow a long way out on Kassandra and around Gerakini and Psakoudia, and many large resorts are built around families, with pools and children's clubs.

Kefalonia works too, but only from the right base: Skala, Lourdas or Xi rather than the steep pebble beaches of the north-west. Melissani and the turtles are good outings for children, though the winding summer drives to reach them can be hard on small passengers. Neither has zoos or theme parks.

Both need a hire car, and in either place the buses are too infrequent to plan a stay around. What slows you down differs. In Halkidiki it is the peninsulas, since getting from one to the next means driving back up to its base. On Kefalonia the roads wind over ridges and along cliffs, so Argostoli to Fiskardo takes about an hour and a half.

Halkidiki is a short run from Thessaloniki airport, at least to Kassandra. Kefalonia has a useful summer ferry across the bay from Argostoli to Lixouri, but parking at Myrtos, Assos and Fiskardo is tight in high season.

Neither is a place to shop. Kefalonia has a little more to browse, on Argostoli's Lithostroto and in Fiskardo's harbour boutiques, while Halkidiki's resort strips sell mostly beachwear, though Thessaloniki is close enough for a proper shopping day. In both, the things worth taking home are local: Robola and mandoles from the island, and olives, honey and the icons and incense of Ouranoupoli from Halkidiki.

Halkidiki is the cheaper of the two. Much of its trade comes from Greek and Balkan families who drive in, which keeps plenty of simple rooms and village tavernas going, although the big Kassandra resorts cost more in high summer.

Kefalonia is mid-priced, with fair value around Skala, Lourdas and Lassi but higher prices in Fiskardo and Assos, and almost every visitor pays for a hire car. In both places, June and September give you the same warm sea for less.

Neither has a year-round stage, but Halkidiki puts on more in summer. The Kassandra Festival brings concerts and theatre to the open-air amphitheatre at Siviri, and the Sani Festival adds jazz and classical evenings.

Kefalonia's offer is smaller and more local. There are the kantades, serenades sung in harmony with guitar and mandolin, and Argostoli's philharmonic band, mostly heard at village festivals and open-air concerts in the town's squares.

Halkidiki has the edge. On the southern tip of Kassandra, the thermal springs at Agia Paraskevi have warm mineral pools above the sea, and the large resorts have well-equipped spas. For quiet, stay on Sithonia or towards Ouranoupoli.

Kefalonia has no bathing tradition and relies on the hotel spas around Lassi, Skala and Fiskardo. You slow down there through long lunches in the hill villages, harbour evenings in Assos and time on the quieter Paliki peninsula.