The change from JAX-RPC to JAX-WS is fundamental, and represents much more than just syntactic sugar. The following comes from Chapter 1 of my book:
"As one example of how the JWS [Java Web Services] specifications have improved, consider JAX-WS 2.0. Chapters 6 and 7 describe that specification in detail, so for now, I'm just going to give a preview of why I think it's such a big improvement over JAX-RPC 1.1. For starters, the JAX-RPC data binding has been removed and the specification has been simplified to focus on the WSDL to Java mapping along with support for REST endpoints. The XML Schema to Java data binding from JAX-RPC has been replaced with JAXB 2.0, a much superior and widely used technology. Second, JAX-WS lets you use annotations to control the shape of the WSDL generated from a Java interface. The use of annotations in this manner simplifies and in some cases eliminates the need for the deployment descriptors required to deploy a JAX-RPC service. Third, JAX-WS provides interfaces (Dispatch on the client side, and Provider on the server side) that enable programmers to directly access and work with XML � effectively bypassing the JAXB data binding when they don't want to use it."