When using Organizations, GitHub Teams is better than GitHub Free because it offers:

GitHub Teams, as part of GitHub’s paid plans, offers additional features and capabilities compared to GitHub Free, particularly for organizations.

GitHub Teams Benefits:

Option B is correct because GitHub Teams provides advanced security features like SAML single sign-on for secure authentication, as well as increased minutes for running GitHub Actions, which are essential for continuous integration and deployment workflows.

Incorrect Options:

Option A is incorrect because private repositories and advanced tools are features available, but the key differentiator in this context is the SAML SSO and additional GitHub Actions minutes.

Option C is incorrect because while expanded storage and priority support are valuable, SAML SSO and increased GitHub Actions minutes are more central to the differences between GitHub Free and GitHub Teams.

Option D is partially correct, but since the question asks for the best reason, Option B provides the most critical features that differentiate GitHub Teams from GitHub Free.