I would say it depends on what you would want to do in the future, both subjects could lead you to a lot of jobs/careers. Also with the french a-level its like gcse english lit but in french as far as I understand so I'm guessing you'd have to be quite confident in French to achieve an A*. At the end of the day I'd say pick the subject you are most confident in - maybe you could look at the specs and see which one you might prefer.