AngularJS: factory and share data between controllers

Question

My question is AngularJS: Why people prefer factory to share data between controllers

 

 

i am new in angular. so trying to know how to share data between two controller and search google. i visited few pages and found most of the time people use factory to share data. i just like to know can't we do it by service instead of factory ?
1st example

<div ng-controller="FirstCtrl">
<input type="text" ng-model="data.firstName">
<br>Input is : <strong>{{data.firstName}}</strong>
</div>
<hr>
<div ng-controller="SecondCtrl">
Input should also be here: {{data.firstName}}
</div>

myApp.factory('MyService', function(){
return {
data: {
firstName: '',
lastName: ''
},
update: function(first, last) {
// Improve this method as needed
this.data.firstName = first;
this.data.lastName = last;
}
};
});

// Your controller can use the service's update method
myApp.controller('SecondCtrl', function($scope, MyService){
$scope.data = MyService.data;

$scope.updateData = function(first, last) {
MyService.update(first, last);
}
});

2nd example

var myApp = angular.module('myApp', []);

myApp.factory('Data', function(){

var service = {
FirstName: '',
setFirstName: function(name) {
// this is the trick to sync the data
// so no need for a $watch function
// call this from anywhere when you need to update FirstName
angular.copy(name, service.FirstName);
}
};
return service;
});


// Step 1 Controller
myApp.controller('FirstCtrl', function( $scope, Data ){

});

// Step 2 Controller
myApp.controller('SecondCtrl', function( $scope, Data ){
$scope.FirstName = Data.FirstName;
});

examples are taken from this url https://stackoverflow.com/questions/21919962/share-data-between-angularjs-controllers

please guide me.