Meteor.Router with and without session params

currently.js

Meteor.Router.add({
  '/posts': 'posts',
  '/posts/:id': function(id) {
    Session.set('postId');
    return 'post';
  },
  '/authors/:id': function(id) {
    Session.set('authorId', id);
    return 'author';
  }
});

Template.post.post = function () {
  return Posts.findOne(Session.get('postId'));
};

Template.author.author = function () {
  return Authors.findOne(Session.get('authorId'));
};

with_params.js

Meteor.Router.add({
  '/posts': 'posts',
  '/posts/:id': 'post',
  '/authors/:id': 'author'
});

Template.post.post = function () {
  return Posts.findOne(Session.get('params').id);
};

Template.author.author = function () {
  return Authors.findOne(Session.get('params').id);
};