AngularJs将公共代码重构为服务

Question

在angularJs中，我有两个控制器，它们有一个共同的功能。我编写一个服务并将这个常用方法投入使用。

以下哪一种方法是正确的，或者有更好的方法可以做到这一点。

1. 通过发送经过修改的$scope个对象来调用公共服务

  angular.module('app').controller('ACtrl', function($scope, $rootScope, MyCommonService) {
            $scope.firstObj = {....};
            //can required more than 4 param
            MyCommonService.doCommontask(firstObj........);
        });

        angular.module('app').service('MyCommonService', function(RestService) 
        {
            this.doCommontask = function (firstObje.......) {
                //following call is to service which do rest call and 
                //almost all work is inside the call back.
                RestService.xxxGET().$promise.then(function(data)
                {
                  // firstObje gets and others modified here and need

                  //value to be reflected in view controlled by ACtrl

                  // most of params of docommonTask used here
                });

            };
        });

1. 调用常用服务并使用$rootScope从controller访问被修改的obj

angular.module('app').controller('ACtrl', function($scope, $rootScope, MyCommonService) {
            //though $rootScope, will only used by this controller and,commonService

            $rootScope.firstObj = {....}; 
            //no param as rootScope is used 
            MyCommonService.doCommontask();
        });

    angular.module('app').service('MyCommonService', function($rootScope, RestService) {
        this.doCommontask = function () {
            //following call is to service which do rest call and 
            //almost all work is inside the call back.
            RestService.xxxGET($rootScope.firstObj...).$promise.then(function(data){
              // firstObje gets and others modified here and need
                 value to be reflected in view controlled by ACtrl
              // most of params of docommonTask used here
            });

        };
    });

要遵循哪一个或者有更好的方法/重构代码哪个有充分的理由？

请建议重构的最佳做法。