Key West or Panama City Beach?

Panama City Beach is the far better place to lie on the sand. It has 43km of powder-white quartz and shallow, clear green water. Key West's beaches are much weaker: Smathers is imported sand, Fort Zachary Taylor's shore is coral rubble, and seagrass flats and washed-up seaweed get in the way of a proper swim.

Key West's strength is the water itself. The reef keeps it calm and it stays warm in winter, which suits snorkelling and boat days. The Gulf at Panama City Beach is only for swimming from late May to October, and its rip currents mean you have to watch the flags.

Both towns eat mostly from the sea, but Key West gives you more to remember. Cuban coffee and sandwiches from takeaway windows, stone crab in season and the long-running argument over Key lime pie give it a character that Panama City Beach lacks. There, fried grouper baskets and the chains on Front Beach Road dominate, with oysters from the nearby bays and a few careful kitchens by the lagoon as the high points.

Key West has a real town to explore, and Panama City Beach has almost none. In Key West, Old Town's conch cottages and Victorian verandas, the Hemingway Home with its six-toed cats, the Truman Little White House and the shipwreck collections tell a story of wreckers, writers and presidents, enough for a couple of days.

The Panama City Beach strip is condo towers and attractions built after the mid-twentieth century. The main exception is the small Man in the Sea Museum on diving history. The older streets of St. Andrews across the bay are the closest it comes to a historic quarter.

Key West makes going out a reason to visit. After sunset on Mallory Square the crowd moves inland to Duval Street's open-sided bars and rooftop decks, which stay open late, and the upper end of the street has a long-established gay scene. Neither town has real clubs.

In Panama City Beach a night out means a frozen drink on a deck over the sand around Pier Park or the lagoon, and outside summer most of the strip is quiet by mid-evening. March is the exception: spring break makes Front Beach Road loud, which suits students and few others.

Both are flat and both spend their outdoor time on the water, but Key West's waters are richer. The Florida Reef is a short boat ride offshore, with turtles and rays. The backcountry flats draw anglers after tarpon and bonefish, and the Dry Tortugas offer remote, clear water and good birdwatching.

Panama City Beach has more to explore on foot. There are the white dunes and pine flatwoods of St. Andrews State Park, a coastal dune lake at Camp Helen and trails in the state forest inland. Its diving is on artificial reefs and wrecks rather than living coral, and dolphin-watching on St. Andrew Bay makes a gentler outing.

Panama City Beach has more within reach, as long as you drive. The planned pastel towns of Seaside, WaterColor and Rosemary Beach along Highway 30A are each under an hour away. The old oyster port of Apalachicola makes a longer day out to the east.

Key West sits at the end of the road, so its one great outing is the ferry to Fort Jefferson in the Dry Tortugas. Beyond that, you can drive over the Seven Mile Bridge to Marathon or Islamorada, small island towns with marinas and a turtle hospital.

Panama City Beach is built around children, and Key West is not. Shallow summer water, condos with pools and kitchens, a water park, a marine park with dolphin shows and go-karts along Front Beach Road will easily fill a week. The St. Andrews lagoon suits small children learning to snorkel. Just avoid March.

For children, Key West offers glass-bottom reef trips, the calm shallows at Fort Zachary Taylor, the butterfly conservatory and the Hemingway cats. Duval Street's early drinking and the adult tone of Fantasy Fest mean families need to choose where they stay with care.

This is the sharpest difference between the two. Key West's Old Town is compact and flat, a rented bike gets you to the bars, the harbour and the sights, and a car is more trouble than help.

Panama City Beach is a long ribbon along one beach road, and you need a car for almost everything. The trolley-buses are slow and sparse, and the pavements come and go with no shade. Summer traffic on Front Beach Road can crawl, though once you have parked, walking along the sand between beach accesses is pleasant.

Neither town is worth visiting for the shopping, but they fall short in different ways. Key West is good for browsing on an evening walk, with Old Town galleries, hand-rolled cigars and sponge shops by the harbour among the Duval T-shirt stores. Panama City Beach is for practical buys, with chain stores and a department store at Pier Park and the shark-mouthed beachwear warehouses. For anything more individual, go to the boutiques in the 30A towns.

Panama City Beach is the easier place to keep costs down. Condos with kitchens let families cook rather than eat out, and outside summer and spring break the rates fall sharply. Car hire is the one cost you cannot avoid.

Rooms in Key West cost far more than in most American towns, because land is scarce and building is restricted, and diving or the Dry Tortugas ferry add to the bill. Walking and cycling everywhere and the free sunset on Mallory Square help, and late summer is the cheapest time to go.

Key West has more live performance, though little of it is formal. Nightly drag cabaret, singer-songwriters in the Duval bars and the sunset street performers on Mallory Square give it a character of its own, while the Tennessee Williams Theatre and a winter symphony season add some substance. Panama City Beach offers cover bands on restaurant decks and summer concerts at the shopping centre, with a restored historic theatre across the bay in Panama City that runs a modest season.

Key West does slow days better, as long as you stay away from Duval Street. Guesthouses set around small pools and gardens on quiet Old Town lanes and the daily pause for sunset make for an unhurried stay, and resort spas and yoga are easy to find.

In Panama City Beach the calm depends on the season. From autumn to spring the empty beach and long sunset walks are restful, but summer and spring break bring the crowds back. Neither town has any bathing or thermal tradition.