Hilton Head or Key Largo?

Hilton Head has the real beach: about 12 miles of wide, hard-packed sand on the Atlantic side. You can choose busy Coligny, family-friendly Driessen and Folly Field, or the quiet stretch in front of Sea Pines. The water is greenish rather than clear, but it is shallow and calm enough for small children to paddle.

Key Largo sits on old coral, not sand, so swimming happens at small man-made beaches in John Pennekamp park, at resort lagoons and off boats. What it gives you instead is warm, clearer reef water that you can swim in through the winter.

Both are simple seafood places with little depth, but Hilton Head has more variety. There is the Lowcountry boil, she-crab soup, shrimp and grits, winter oyster roasts and May River oysters, plus a more local set of kitchens in Old Town Bluffton.

Key Largo keeps to fresh fish from local boats: snapper, grouper and mahi-mahi served grilled, blackened or in sandwiches on docks along the highway, with conch fritters and Key lime pie. Anything more ambitious means driving to Miami.

Neither is a place for sightseeing, but Hilton Head has a story to tell. The Gullah heritage at Mitchelville Freedom Park, the Coastal Discovery Museum and the plantation ruins make for worthwhile short visits.

Key Largo's sights are curiosities more than history: the boat from The African Queen at a marina and the Christ of the Abyss statue, which you can only see from the water.

Both go quiet early. On Hilton Head a night out means waterfront decks with a cover band around Coligny and the marinas, full of families and golfers in summer. Key Largo's evenings centre on bay-side tiki bars with a guitarist at sunset, and they empty early because the dive boats leave at dawn. For anything bigger, Key Largo has Miami about an hour and a half away by car.

This is Key Largo's great strength. John Pennekamp protects shallow reefs such as Molasses and French Reef for snorkellers, and the sunken Spiegel Grove draws deeper divers. On the bay side there are mangrove channels, manatees and crocodiles, and the Everglades lie just across the water.

Hilton Head's outdoors is gentler and stays on dry land more often. You can paddle the spartina marsh, watch dolphins in Calibogue Sound, see herons and alligators on Pinckney Island and cycle more than 60 miles of paths under live oaks.

Hilton Head is far better placed. Savannah's historic district is about 45 minutes away, Beaufort's antebellum mansions are under an hour, the bridgeless island of Daufuskie is a short ferry ride, and Charleston makes a long but rewarding day.

From Key Largo the main outing is Miami, for South Beach and Little Havana. Islamorada, Marathon's sea turtle hospital and Coral Castle are smaller stops, and Key West is too far to do comfortably in a day.

Hilton Head is the stronger family choice overall, and it works for every age down to toddlers. Days fill themselves close to the villa: the playground beside the Harbour Town lighthouse and its summer evenings of children's entertainment, mini golf, resort pools, dolphin cruises and the butterfly house at the Coastal Discovery Museum. There is no zoo or theme park, and summer afternoon thunderstorms need planning around, but little else gets in the way.

Key Largo's appeal is narrower and mainly for children old enough to snorkel. For them, a glass-bottom boat over the shallow reef, the small aquarium at the John Pennekamp visitor centre and the dolphins and sea lions at the long-established marine park in Islamorada make memorable days. Younger children have far less to do, and summer brings mosquitoes and the hurricane season, so families mostly come in winter and spring.

You will want a car in both, but Hilton Head lets you leave it parked. Once you have arrived from Savannah's airport, the bike paths link beaches, shops and villas, and you can ride on the sand at low tide. The one main road and the gated communities are the drawbacks.

Key Largo stretches about 30km along the Overseas Highway with few pavements, so even dinner means a drive. Most of the day's travel happens on dive and tour boats that leave from marinas near where you stay.

Hilton Head has more to browse. The open-air villages at Coligny, Shelter Cove and Harbour Town have galleries and resort wear, the Bluffton outlets are useful on rainy days, and Gullah sweetgrass baskets make a souvenir with real meaning. Key Largo has little beyond roadside souvenir stands and good dive and fishing shops.

Both are costly American resorts, and the extras add up: golf and boat trips on Hilton Head, dive and fishing charters on Key Largo. The difference is when they are expensive. Hilton Head peaks from June to August and is cheaper in spring and autumn, while Key Largo is dearest from December to April. In both, you can save by staying inland, in Bluffton or in Homestead and Florida City, if you accept a daily drive.

Hilton Head has a modest but real calendar. The Arts Center of Coastal Carolina puts on theatre and musicals, the island's symphony orchestra plays a winter season, and there are jazz and Gullah festivals and free summer concerts at Harbour Town. Key Largo has a guitarist on a bar deck and a small community theatre, and everything else means Miami.

Rest takes a different shape in each. On Hilton Head it comes from bike rides under the live oaks, beach walks in the quiet off-season months and evenings by the marsh. Treatments are not confined to your hotel either: day spas and yoga studios are spread around the island, and there is a grand riverside resort spa near Bluffton.

On Key Largo, relaxing happens almost entirely at the resorts. The larger bay-side ones have hammocks, lagoon pools and full spas, yoga on a dock is easy to find, and there is little beyond that. Stay on the bay side, away from the highway that runs through the middle of the island, and remember that neither place has a tradition of thermal bathing.