javascript - Performance of $rootScope.$new vs. $scope.$new -

my current controllers $scope kind of thick with: $watch , event handlers.

on 1 point need create new scope modal, not have own controller, because quite simple. still needs property of current $scope. wondering of following solutions better, , why?

a)

var modalscope = $rootscope.$new(); modalscope.neededvalue = $scope.neededvalue; 

b)

var modalscope = $scope.$new(); // modalscope.neededvalue there 

should worried created modalscope watch expressions , events? other aspects should aware of?

option a) copies value once , doesn't keep in sync $scope, may cause confusing bugs. if modal has deep scope hierarchy there cases option a) might give slight performance advantage (calling $broadcast on $scope means needs cover smaller scope tree), in i'd option b) way go.

your $watches won't benefit location of scope unless you're $digesting particular scope.

edit: see modal light, in case, go option b), performance advantage a) negligible.