WCF Vs Webservices - Why We Use WCF

1 File Format/Extension :
i) ASP.net service - '.asmx'
ii) WCF service - '.svc'

2 Hosting :
i) ASP.net service - Can be hosted in IIS also can be hosted in a Windows Service.
ii) WCF service - Very flexible, can be hosted in IIS, Windows Activation Services(WAS), Managed Windows Services and It also supports Self-Hosting.

3 Transport Protocols/Binding :
i) ASP.net service - It supports HTTP & TCP protocols along with custom binding.
ii) WCF service - supports HTTP, WS-HTTP, TCP, Custom, Named Pipes, MSMQ & P2P(Point to Point) etc.

4 Data Transformation :
i) ASP.net service - XML serializer for Data Transformation.
ii) WCF service - DataContractSerializer for Data Transformation.

5 Serialization NameSpace :
i) ASP.net service - System.XML.Serialization
ii) WCF service - System.RunTime.Serialization

6 Supported Operations :
i) ASP.net service - only One-Way and Request-Response type.
ii) WCF service - Includes One-Way, Request-Response and Duplex.

7 Encoding :
i) ASP.net service - It uses following encoding mechanisms - 
XML1.0, MTOM (Message Transmission Optimization Mechanism), DIME (Direct Internet Message Encapsulation)
ii) WCF service - It uses following encoding mechanisms - 
XML1.0, MTOM, Binary

Tag:-difference between Webservice and WCF,WCF vs Webservice,About WCF,WCF Features