WCF is the ideal choice when you need to create a service that supports unique scenarios such as duplex communication, one way messaging and message queues, among others. Web API should be the option when you need to build resource-oriented services over HTTP that can utilize the full features of HTTP.

If you want any service wants to support multiple platform like http and tcp id based , then we will go for WCF service , because same service will exposed with different service, whereas the webapi will support only http based protocol.