1.) SOAP relies exclusively on XML to provide messaging services.
2.) SOAP has some rigid set of messaging patterns than REST.
The rules in SOAP are important because without these rules,
you can’t achieve any level of standardization.
3.) SOAP is designed to support expansion, so it has all sorts of other acronyms and abbreviations associated with it, such as WS-Addressing, WS-Policy, WS-Security, WS-Federation, WS-ReliableMessaging, WS-Coordination, WS-AtomicTransaction, and WS-RemotePortlets.
4.) REST as an architecture style does not require processing and is naturally more flexible.
One of the most important SOAP features is built-in error handling. If there’s a problem with your request, the response contains error information that you can use to fix the problem.
5.) REST provides a lighter weight alternative. Instead of using XML to make a request, REST relies on a simple URL in many cases.
7.) REST requires expensive tools require to interact with the Web service.
8.) Since there is no additional processing required, REST is faster than SOAP.