Cozumel or Riviera Maya?

Both have the same warm, clear Caribbean, but the mainland has the beaches. More than 100km of white sand runs from Puerto Morelos to Tulum, with calm, reef-sheltered bays at Akumal and Xpu-Ha and the much-photographed beaches below Tulum's ruins.

Cozumel's sheltered west coast is mostly low limestone rock, and its sand is largely run as beach clubs south of San Miguel. The wild east coast is too rough for swimming. What makes up for it is reef a few strokes from shore, so a beach day there is mostly a snorkelling day.

On both sides of the channel the cooking is Yucatecan: cochinita pibil, panuchos, ceviche and fish from the morning boats. The Riviera Maya has much more range, with backstreet taquerias in Playa del Carmen and Tulum town and a row of ambitious wood-fired restaurants on Tulum's beach road.

Cozumel eats simply. There are family places behind San Miguel's waterfront, taco stands on the square in the evening and the market for breakfast, while the seafront is given over to Tex-Mex for cruise passengers.

Neither is a place to go for culture, but the mainland has the bigger ruins. Tulum's walled city on its cliff and the tall pyramids and raised roads of Coba give the Riviera Maya real Maya sights, and Muyil on the edge of Sian Ka'an adds a third.

Cozumel's own site, San Gervasio, is low and scattered in the forest. It recalls the island's pilgrimages to Ixchel rather than impressing by its size. The waterfront museum and the Punta Sur lighthouse complete a short list, and neither destination has a historic town centre.

This is one of the widest gaps between them. Playa del Carmen's clubs and rooftop bars around Calle 12 keep going past 3am, and Tulum is known for electronic music in jungle clearings and beach clubs, busiest in winter.

Cozumel keeps divers' hours. San Miguel has a few bars with cover bands and some terraces, liveliest while cruise passengers are ashore, and after that it is a quiet drink. Anyone wanting a club takes the ferry over to the mainland.

Both lie on the Mesoamerican Reef, and Cozumel's drift walls at Palancar, Santa Rosa and Columbia are its most famous stretch, a short boat ride from the island's hotels. If diving is the whole point of the trip, the island puts you closest to it.

Beyond the reef, the mainland is far richer. It has cenotes such as Dos Ojos and Gran Cenote for snorkelling and cave diving, turtles in Akumal's bay and boat trips into the lagoons and mangroves of Sian Ka'an. On land Cozumel offers flat scrub, Punta Sur's lagoons and a windy east coast to cycle along. Neither has any hills.

Every day trip from Cozumel starts with the ferry to Playa del Carmen. That makes Tulum, Coba or the cenotes a long day with a crossing at each end, and Chichen Itza needs a night on the mainland.

From the mainland coast those same places are a short drive away. Chichen Itza with colonial Valladolid, or quieter Ek Balam, becomes a realistic day out with an early start. Cozumel itself and Isla Mujeres are easy boat trips.

The Riviera Maya is the easier choice with children. It has resorts with kids' clubs and shallow pools, sandy reef-sheltered bays at Akumal, Xpu-Ha and Puerto Morelos, and eco-parks with underground rivers and zip lines. The ruins at Tulum and Coba are short enough for young legs.

Cozumel works for families with older children who snorkel. There is the calm west coast, Chankanaab's lagoon and sea lions, and semi-submarine boats for non-swimmers. Sharp ironshore and little else built for children make it harder going with toddlers.

Cozumel has a single paved road looping the island, so a day with a hire car or scooter covers everything. Fixed-fare taxis and dive operators' hotel pickups fill the gaps, but there is no public transport worth relying on.

The Riviera Maya is more spread out but better served. Buses link the airport, Playa del Carmen and Tulum, and colectivo vans stop on request all along the highway. Taxis there are expensive, though, and a car is still the easiest way to reach Coba and the cenote roads.

Neither is worth a trip for shopping. Cozumel's is port shopping: duty-free jewellers, silver and tequila along the San Miguel waterfront, a hard sell on cruise days and a few better craft shops on the side streets.

The Riviera Maya has more to browse, from the long Quinta Avenida in Playa del Carmen to the linen, baskets and design boutiques of Tulum. For embroidered huipiles and pottery, Valladolid inland beats both.

Cozumel is the cheaper of the two. Small guesthouses and dive hotels in San Miguel, the market and the taco stands keep daily spending modest. The real cost is the diving, which adds up over several days of boat trips.

On the Riviera Maya, prices are set for international visitors, and Tulum's beach hotels and restaurants are expensive by any measure. The thrifty way to do the coast is to stay a few blocks back from the sea in Playa del Carmen or Puerto Morelos and travel by colectivo.

There is little stage life in either place, and neither has a theatre or concert hall. The Riviera Maya has a little more to see: evening shows of Maya ball games and folk dance at the eco-parks, and live Latin, reggae and rock bands in the bars of Playa del Carmen and Tulum.

Cozumel's one real occasion is its carnival before Lent, one of the oldest in Mexico. The rest of the year it is mariachis on the square and folk dance at resort dinners.

The Riviera Maya is made for this. Tulum has jungle yoga shalas, retreats and sound-healing sessions, the coast offers temazcal sweat lodges and cenote swims, and the resorts have some of the largest hotel spas in Mexico. For quiet, stay in Puerto Morelos, Akumal or at the southern end of Tulum's beach road.

Cozumel relaxes you through its slow pace rather than its facilities. There are adults-only resorts on the southern strip and the empty east coast for watching the surf. The spas offer the usual resort massages, and only a few places run a temazcal.