We are looking at switching from using WCF for our service layer in applications to REST.
So far we are assuming that the way to do this is to use the WCF REST Start
We were building an app to consume our existing services. We also had a requirement to implement RESTful services but our main goal was to reuse/centralise our already existing WCF services, achieving reusability.
We then tried out the Web API and found it quite straight forward. It also provided us an additional layer to our architecture that we could also control.
We had performance concerns at first but so far, those have been quite minimal.
So, if you do not mind adding an additional layer on your WCF services, let it exist as a Web API layer, otherwise HttpClient is equally solid as an option.