Whilst JavaCAPS6, and specifically the HTTP Binding Component, have
many useful features, there are currently limitations with it, notably
calling JAX-RPC webservices using soap encoded arrays and calling
webservices using SOAP1.2.
With JAX-WS you get access to the Dispatch API which makes it easy to call both of these use-cases from Java code.
the Dispatch code inside an EJB, exposed as a doc/literal webservice,
is a simple way to create a proxy to these external webservices, this
EJB-WS can then be called from BPEL, for example, via the JavaEE SE
making the overall process very efficient.