Rest is preferred over soap because

• REST can use JSON,XML or HTML as messaging formats to transfer the data,while soap can use only XML
• REST use only URI to expose the service to outside world,where SOAP needs to expose the service interfaces
• When SOAP HTTP as transport layer,it can use only POST method,while REST can use all 4 HTTP methods like GET,POST,PUT,DELETE.
• REST is quicker than soap

Advantae of SOAP over REST is SOAP is more secured than REST and can use HTTP,SMTP and other transport protocols,where as REST depends on HTTP protocol alone.