Why to use WCF service

I would say, not quite. You cannot assume anything about the possible application, and I would guess this is pure study. Client-server can be considered in the widest sense of this term. And then WCF has apparent benefits. It still can use HTTP, but the channels can be easily replaced with the channels using other protocols, without any change in application code. Besides, WCF solution can be much, much lighter; for example, it can be self-hosted. Using ASP.NET can only be justified if the HTTP server is used for something else, say, serving up ASP.NET with IIS. In general case, this is not so. Aren't you biased to ASP.NET because you do Web development? But out inquirer started with Windows application. So why?

So, in general case, I would strongly recommend WCF.

—SA

Not really, I left ASP.NET when 2 years ago I heard you say, "I don't do web." I don't build web applications at all, and personally I was also trying to communicate from a desktop approach.

The major benefit of ASP.NET Web API over WCF is that you can use it in any framework at all, no need for ClientBase stuff. Besides, who wants to use SOAP, when you can do things in JSON, with smaller size over network.

I have also made applications where data is backed up on a network hosted database, somewhere on external network. WCF doesn't play fair, when you want to support devices that cannot run .NET framework. Linux environment for example, much more... JSON-formatted content from Web API would be much better than using SOAP or other ones that WCF supports.

Now, I am willing to give WCF another try to see if it can beat ASP.NET Web API. :-)

All right. "Who wants to use SOAP" can be replied: Who wants to use SOAP? It's one of the worst XML formatters from the set of all widely used ones. But WCF can use any... and so on...
—SA