Well most of the time unit tests are used for small units and features are used for more integration tests. For example when you want to test a relationship you need to write a feature test because it uses a database to properly test it. For example an algorithm is a unit test because you test a small independent feature!
However in Laravel you can also perform unit tests using the database depending on the class you extend. For example extending the TestCase class is a feature in general. However if you extend the PHPUnit\Framework\TestCase it's a real unit test because it has no knowledge of Laravel.
So in general I would keep the role that if the test is Laravel independent it's a unit test and otherwise a feature test!
Hope that helps a bit!