For a law degree which of these two a levels would be better. My other two Alevels are Psychology and History.
You already have at least one essay-based subject, so it doesn't matter which is your third A level - Law has no specified subject requirements (but at least one essay-based subject is useful).
You already have at least one essay-based subject, so it doesn't matter which is your third A level - Law has no specified subject requirements (but at least one essay-based subject is useful).