Why use XML-RPC instead of SOAP?
If your clients and servers are all running in the .NET environment there is no point in using XML-RPC: .NET provides excellent support for SOAP and XML-RPC doesn’t have any features not provided by SOAP (other than simplicity). If you use .NET clients and want to connect to XML-RPC servers running under any OS then XML-RPC.NET is a good choice. If you want to implement a server in the .NET environment which is to be connected to by clients running in other environments, say Unix or Java, then XML-RPC may be an appropriate choice. SOAP is supported in many different environments but is considerably more complicated than XML-RPC and presents more opportunity for interop problems.