$watch a service variable or $broadcast an event with AngularJS

$watch a service variable or $broadcast an event with AngularJS

I'm using a service to share data between controllers. The application has
to update the DOM when a variable is modified. I've found two ways to do
that, you can see the code here:
http://jsfiddle.net/sosegon/9x4N3/7/
myApp.controller( "ctrl1", [ "$scope", "myService", function( $scope,
myService ){
$scope.init = function(){
$scope.myVariable = myService.myVariable;
}; } ] );
myApp.controller( "ctrl2", [ "$scope", "myService", function( $scope,
myService ){
$scope.increaseVal = function(){
var a = myService.myVariable.value;
myService.myVariable.value = a + 1;
}; } ] );
http://jsfiddle.net/sosegon/Y93Wn/3/
myApp.controller( "ctrl1", [ "$scope", "myService", function( $scope,
myService ){
$scope.init = function(){
$scope.increasedCounter = 1;
$scope.myVariable = myService.myVariable;
};
$scope.$on( "increased", function(){
$scope.increasedCounter += 1;
} ); } ] );
myApp.controller( "ctrl2", [ "$scope", "myService", function( $scope,
myService ){
$scope.increaseVal = function(){
myService.increaseVal();
};} ] )
In the first case, I share a variable from the service with the controller
and $watch it in the directive. Here, I can modify the variable directly
in this controller, or any other controller that share it, and the DOM is
updated.
In the other option, I use a function from the service to modify the
variable which $broadcast an event. That event is listened by the
controller, then the DOM is updated.
I'd like to know which option is better and the reasons for that.
Thanks.