I'm a little confused about which way I should create a new AngularJS application. As far as I can tell there seems to be a couple of ways to do it, either using angular-seed: https://github.com/angular/angular-seed
or
yeoman - http://www.sitepoint.com/kickstart-your-angularjs-development-with-yeoman-grunt-and-bower/
What I can't find is any resources on why you would choose one method over the other. The resulting directory structures look quite different to me. Is it correct to say that one of the main differences is that angular-seed doesn't use Bower or Grunt out of the box, whereas a yeoman generated application does?
If I used angular-seed and wanted to add grunt to it then I am guessing this would be a bit of a manual process?
Definitely use Yeoman. It gives you more than just a project structure out of the box (it has tasks for tests and building all ready to go). However, it's debatable which yeoman generator to use. It really depends on the project. I would suggest one of these:
Simple Project: https://github.com/yeoman/generator-angular
Large Project: https://github.com/cgross/generator-cg-angular