In the United States, a CV is almost exclusively limited to professions in academia, science and medicine. In the case of academia, the main focus of the CV should be to identify yourself as a scholar. The added length, should be filled with proof of your skills as a teacher, scholar, and your knowledge of education. A CV should be thought of as a living document, and it will change frequently based on the updates in your education and career.
Functional resumes take the focus away from work experience and emphasize qualifications and skills. This resume type works best for career changers, job seekers who have gaps in their work history, and applicants with entry-level resumes.