Nested Routes vs Model Relations

http://discuss.emberjs.com/t/deep-nested-routes/659

HTML

<!DOCTYPE html>
<html>
<head>
  <title></title>
  <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.js">
  </script>
  <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/handlebars.js/1.0.0-rc.3/handlebars.js">
  </script>
  <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/ember.js/1.0.0-rc.1/ember.js">
  </script>
  <script type="text/javascript" src="http://dl.dropbox.com/u/74115264/ember/ember-data.js">
  </script>
  <script type="text/javascript">
    // Splash image courtesy: http://www.flickr.com/photos/chavals/2869153410/

    var App = Ember.Application.createWithMixins({
      LOG_TRANSITIONS: true,
      init: function () {
        this.deferReadiness();
        this._super();
      }
    });

    App.Router.map(function () {
      this.resource('projects');
      this.resource('project', {path: '/projects/:project_id'});
      this.resource('iteration', {path: '/iterations/:iteration_id'});
      this.resource('task', {path: '/task/:task_id'});
    });

    App.IndexRoute = Ember.Route.extend({
      redirect: function () {
        this.transitionTo('projects');
      }
    });

    App.ProjectsRoute = Ember.Route.extend({
      model: function () {
        return App.Project.find();
      }
    });

    App.Store = DS.Store.extend({
      revision: 11,
      adapter: 'DS.FixtureAdapter'
    });

    App.Project = DS.Model.extend({
      name: DS.attr('string'),
      iterations: DS.hasMany('App.Iteration')
    });

    App.Iteration = DS.Model.extend({
      name: DS.attr('string'),
      project_id: DS.attr('number'),
      project: DS.belongsTo('App.Project'),
      tasks: DS.hasMany('App.Task')
    });

    App.Task = DS.Model.extend({
      name: DS.attr('string'),
      iteration_id: DS.attr('number'),
      iteration: DS.belongsTo('App.Iteration')
    });

    App.Project.FIXTURES = [
      {
        id: 1,
        name: 'Project Curiosity',
       ...