In an interview, I was asked this question.
According to me, both are actually exposing a service.
If it takes n amount of time to scale a .net solution which implements a SOAPful service then shouldn't it take the same n amount of time to scale a .net solution which implements RESTful service?
Short answer: S in REST stands for stateless, but you can make REST just as hard to scale as SOAP.
In time, I think your question is a duplicate of this. Have you searched before posting?