WWN zoning groups a number of WWNs in a storage-area network zone and allows them to communicate with each other. The switch port that each device is connected to is irrelevant when WWN zoning is configured. An advantage to this type of zoning is that if a port is suspected of being faulty, another port can be used without the need for fabric reconfiguration. A disadvantage with WWN zoning is that if there's a host bus adapter (HBA) failure, the fabric will need to be reconfigured for the host to reconnect to its storage. WWN zoning is sometimes referred to as soft zoning.
Port zoning groups particular switch ports together to allow any device connected to those ports to communicate with each other. The advantages and disadvantages of port zoning are the opposite of those for WWN zoning.
I don't believe either type of zoning is superior to the other, so the type of zoning used is often determined by what a particular consultant or organisation has used in the past.
For more on zoning:
1. Read the definition of zoning
2. Learn why you should zone in Zoning 101
3. Discover the differences between hard zoning and soft zoning