The REST API is a very generic API and allows you to manipulate contents using CRUD operations and some other features of Alfresco.
Typically each call is done using standard HTTP methods and JSON or XML as input and output format for metadata.
It is not ever suitable and easy to use the standard REST API of Alfresco, it depends on your needs.
But if you need to implement specific features that work on contents using many features of Alfresco, it could be very straightforward to adopt the WebScripts way.
This because using WebScripts you can extend the REST API of Alfresco using your own REST implementation at the Alfresco back-end side.
This is very useful because you can make savings of HTTP calls: in an unique HTTP call you can encapsulate a segment of operations that otherwise, using the standard REST API, it would otherwise require several calls.
If you need that you client application must be suitable for any CMIS repository, then I suggest to implement your interface using Apache Chemistry adopting the OpenCMIS library as your client library.
Anyway in the Alfresco you can find many examples of WebScripts and you could take a look at these examples to understand how to extend the REST API with your own custom interface.
I suggest to take a look at my book about WebScripts, SOAP API and CMIS to understand what is the best way to follow for your project.
Hope this helps :wink: