Cancun is an airport that services much of the Yucatan Pennisula.  The areas in and around Cancun are all very different and depending on what you are looking for in a vacation, may change where you want to stay.  If  staying in Isla Mujeres, Playa Del Carmen Puerto Morelos, Akumal or  down in Tulum, Cancun is the nearest airport.  Cozumel has an airport with ferry service to Playa.

Resorts and hotels in Cancun "proper" are generally located on a public beach.  If you don't mind the vendors interrupting your sun-bathing, book-reading or siesta then you will enjoy the beautiful white sand beaches.  In addition, based on the time of year you are there, you may find the beaches to be more crowded.  Stay in Cancun if you want to be close to nightlife and shopping.  There will be plenty to do, but not necessarily the place you want to stay if you are looking for a quiet, relaxing vacation.

Playa del Carmen is located south of Cancun along the Yucatan Pennisula.  Playa is a much smaller atmosphere than Cancun with a moderate amount of night life, shopping and restaurants along 5th Avenue and into the surrounding neighborhoods.   Boutique hotels, a few all-inclusive and reasonably priced hotels line the beach.  If not staying on the beach,   palapa and chair rentals are available at beach clubs.

Between the two, is the Riveria Maya.  Located directly across the ocean from Cozumel you will find that the waves aren't as big and beaches more private.  There is a coral reef located in the waters between Cozumel and the mainland which causes the beach to be a bit less friendly for barefoot walking.  This area is also less developed than either Cancun or Playa which means the beaches for the resorts are very private.  You won't be able to walk for miles and miles along the beach, but with a pair of water socks can have a fun adventure too  All-inclusive resorts, luxury and boutique hotels can be found all along the coast.

Make your choice of location stays based on what you're looking for!