Usually,
WebAPI used for data services where MVC can generate more types of outputs.
WebAPI for sure simplifies the way we can create data services.
It's clean and easy for this purpose.
MVC come with some more tools around.
MVC can generate any output WebAPI can output.
Generating outputs from templates can be easily achieved in MVC. I can't find a reason to do so in WebAPI. PHP developers and old ASP programmer might know this attitude from the past, where you can build HTML files involved with C# code inside.
WebAPI- DATA
MVC - DATA, UI/HTML, XHTML, Files, Templates etc..
