Good articles to understand difference in SOAP and REST. These will help to understand where you should use SOAP/REST

[REST vs SOAP][1]

[REST vs SOAP using http][2]
[1]: http://www.ajaxonomy.com/2008/xml/web-services-part-1-soap-vs-rest
[2]: http://geeknizer.com/rest-vs-soap-using-http-choosing-the-right-webservice-protocol/