From your initial description it sounded like you were talking about having the exact same image in both places. If that is the case, then there is no telling them apart, and which is used doesn't really matter. If you are talking about say, an old release on the recovery partition and a new release in the dvd, that would be something different.
From your initial description it sounded like you were talking about having the exact same image in both places. If that is the case, then there is no telling them apart, and which is used doesn't really matter. If you are talking about say, an old release on the recovery partition and a new release in the dvd, that would be something different.