Is there GCM(Google Cloud Messaging) have any advantage over web service communication in android programming

I like to write a program in android that sent notification from web to android application. I hear that there are two types of communication is possible in Web to android. One is Using GCM and (Google Cloud Messaging) and other is using Web service communication. so is there GCM(Google Cloud Messaging) have any advantage over web service communication in android programming.