How to inject references in angularjs unit test

I saw two different ways of injecting references in unit tests.

Underscore Wrapping

beforeEach( inject( function(_myService_){
  myService = _myService_;
}));

or

$injector injection

beforeEach(inject(function($injector) {
  myService = $injector.get('myService');
}));

What are the differences? Which one is the best practice?