Marco Island or Naples, Florida?

These are equally strong beach destinations, and the Gulf is the same calm, shallow, warm water off both. What differs is the shape of the shore. Marco Island has one broad, curving crescent, wide at low tide for shelling walks, with the tidal lagoon and sandbar at Tigertail for wading and the undeveloped barrier beach of Keewaydin a short boat ride away.

Naples has a long, narrow strip running the length of the town, reached by paths at the ends of residential streets in Old Naples, with the pier as its social centre. Its wilder stretches lie to the north at Clam Pass, Delnor-Wiggins and Barefoot Beach.

Both eat from the same Gulf menu of grouper sandwiches, shrimp, oysters and winter stone crab, but Naples has more to choose from. Marco Island leans on waterfront grills, resort dining rooms and the dockside fish shacks of Goodland, and beyond seafood the range quickly runs out.

Naples adds whole streets of white-tablecloth restaurants, terraces and wine bars on Fifth Avenue South and Third Street South, plus the fish houses around Tin City. It is still polished rather than adventurous, but it is where island visitors go for a special dinner.

Neither is a place to travel for sightseeing, but Naples has enough to fill a day and Marco Island hardly has a morning's worth. The island's one real stop is its historical museum, which covers the Calusa people, the carved wooden figures found here in the 1890s and the island's clam-cannery past.

Naples adds the Baker Museum's modern and American art, the Revs Institute's historic racing cars, Palm Cottage, the old railway depot and the Mediterranean-style streets of Old Naples. That makes a modest but pleasant change from the beach.

Evenings are quiet in both and end early, with a sunset drink and dinner rather than a night out. On Marco Island the liveliest moments come from the resort lounges, the marina bars and Goodland's dockside crowd on winter weekend afternoons. Naples offers a slightly more dressed-up evening, with piano lounges and wine bars along Fifth Avenue South and tiki bars at the beach.

Both look onto the same wetland wilderness, but Marco Island puts you closer to the water. It sits at the northern tip of the Ten Thousand Islands, so mangrove paddling, dolphin trips, manatees in the canals and some of Florida's best inshore fishing begin at the island's edge, and Rookery Bay and the Tigertail bird flats are close by.

From Naples the same landscapes are a drive away, though the city has easier access to Corkscrew Swamp Sanctuary's cypress boardwalk. Either way, Big Cypress and the western Everglades are within an hour.

Neither is a base people choose for its excursions, and both draw on the same short list, so the real difference is which way you face. Marco Island sits at the southern end, where the roads give out into the swamp. Everglades City, the island settlement of Chokoloskee with its old trading post, and the airboats and boardwalks of Big Cypress are noticeably closer than they are from Naples. The towns all lie north, though, and for island visitors Naples itself becomes the main town outing, for its pier, galleries and a better dinner.

Naples is the better starting point for the coast to the north. From there the Edison and Ford Winter Estates in Fort Myers, the shelling islands of Sanibel and Captiva and the Ringling museums in Sarasota are all within easier reach, and Marco Island's broad beaches make a short run south.

Both rely on the same gentle, shallow Gulf for young children, but Naples has more for families once they leave the sand. Marco Island offers wading at the Tigertail lagoon, shelling, dolphin boat trips and resort kids' clubs, and very little built for children beyond that.

In Naples the zoo with its primate-island boat tour, the Golisano Children's Museum and the children's garden at the botanical garden are all close by. That makes a hot or stormy afternoon much easier to fill, and island families end up driving there for the same outings.

You will want a car in either place, and the difference lies in what you can do without one. Marco Island is small and flat with cycle paths along its main roads, so bikes work well between the beach, plazas and restaurants. Naples has a compact, walkable centre in Old Naples, where staying near the pier puts the sand, dinner and shops within a walk, though the rest of the city sprawls along wide roads.

Naples is clearly the place to shop, and Marco Island visitors know it. The island has a few small plazas of resort wear, beach gear and shell-themed souvenirs.

Naples has palm-shaded Fifth Avenue South and Third Street South with jewellers, galleries and linen boutiques, a luxury open-air mall north of downtown, the converted clam sheds of Tin City and outlet malls a short drive away.

Neither is cheap, and both are at their dearest from January to April, when the winter crowd fills the beachfront rooms and the restaurants. The ways to save differ. On Marco Island, weekly condo rentals with kitchens help families and groups. Naples gives more options for staying inland in chain hotels or up the road in Fort Myers, and in both the hot summer brings much lower rates.

Naples has a real winter arts calendar, with the Naples Philharmonic in its own hall, touring Broadway shows, chamber music, a professional theatre company and jazz nights in restaurants. Marco Island offers a small community theatre and a guitarist in the resort bar, and its visitors drive north for anything more. In both, the programme largely disappears in summer.

Rest comes from the slow pace in both, as neither has a bathing tradition. Marco Island feels more removed, an island of quiet canals where the resort spas look straight over the Gulf. Naples mixes its resort and day spas with golf, long sunset walks along the beach, and spas that welcome non-guests.