The application of semantics in Web Services as Semantic Web Services for dynamic discovery, composition, invocation and monitoring has been very helpful in enabling Enterprise Application Integration and E-Commerce. There are many initiatives that aim to realize the Semantic Web Services to enable effective exploitation of semantic annotations, and two major of them are Web Service Modeling Ontology (WSMO) and Ontology Web Language for Services (OWL-S). Several tools have been developed to realize both the conceptual models i.e. Web Services Execution Environment (WSMX) is the reference implementation for WSMO, on the other side OWL-S reference implementation exists in the form of loose collection of individual tools like OWL-S Editor, OWL-S Matchmaker, OWL-S Virtual Machine, OWL-S IDE, WSDL2OWL-S converter and OWL-S2UDDI converter etc. In this paper, we have conducted a comparison of both the reference implementations to identify similarities and differences between them and to evaluate their potential to become widely accepted implementation recommendations.