Webservice?
Webservice use SOAP (Simple Object Access protocol) and it is used to
  connect the web application using different type of technologies, and
  possible to connect the application that have hosted in different type
  of servers.
Disadvantage of Webservice
Webservice use only HTTP Protocol. It provides only singlex
  communication, not half duplex and full duplex communication. They
  work in an stateless fasion over HTTP and are hosted inside a web
  server like IIS
Advantages of WCF Service
WCF Service support  HTTP, TCP, IPC, and even Message Queues for
  communication. We can consume Web Services using server side scripts
  (ASP.NET), JavaScript Object Notations (JSON), and even REST
  (Representational State Transfer). It can be configured to have
  singlex, request-response, or even full duplex communication. These
  can be hosted in many ways inside IIS, inside a Windows service, or
  even self hosted.
Half duplex
Half-duplex data transmission means that data can be transmitted in
  both directions on a signal carrier, but not at the same time.
  half-duplex transmission implies a bidirectional line (one that can
  carry data in both directions).
They work in an stateless fashion over HTTP and are hosted inside a web server like IIS
Full duplex
Full-duplex data transmission means that data can be transmitted in
  both directions on a signal carrier at the same time. Full-duplex
  transmission necessarily implies a bidirectional line (one that can
  move data in both directions).