I would go with second one, from angularjs wiki
Scope inheritance is normally straightforward, and you often don't
even need to know it is happening... until you try 2-way data binding
(i.e., form elements, ng-model) to a primitive (e.g., number, string,
boolean) defined on the parent scope from inside the child scope. It
doesn't work the way most people expect it should work. What happens
is that the child scope gets its own property that hides/shadows the
parent property of the same name. This is not something AngularJS is
doing – this is how JavaScript prototypal inheritance works. New
AngularJS developers often do not realize that ng-repeat, ng-switch,
ng-view and ng-include all create new child scopes, so the problem
often shows up when these directives are involved. (See this example
for a quick illustration of the problem.)
This issue with primitives can be easily avoided by following the
"best practice" of always have a '.' in your ng-models – watch 3
minutes worth. Misko demonstrates the primitive binding issue with
ng-switch.
Having a '.' in your models will ensure that prototypal inheritance is
in play. So, use
<input type="text" ng-model="someObj.prop1"> rather than
<input type="text" ng-model="prop1">.
If you really want/need to use a primitive, there are two workarounds:
Use $parent.parentScopeProperty in the child scope. This will prevent
the child scope from creating its own property. Define a function on
the parent scope, and call it from the child, passing the primitive
value up to the parent (not always possible)
https://github.com/angular/angular.js/wiki/Understanding-Scopes