REST is easier than SOAP, REST is more of a convention for structuring all of your methods, REST works more like you'd expect browser URLs
- When you want to return output in XML and JSON format
basically, it is depend upon What is your service abstracting from the client? What is the level of security required? Is your service a long running asynchronous process? And many other requirements will increase the level of complexity. Testability.
In all above scenario, apparently it easier to test RESTFul web services than their SOAP counter parts
REST is useful when to concentrate on Caching, HTTP Verb Binding, Security etc
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]