Yes, there is an advantage to backing up to the E drive. Twice I've had customers think they want to try some programming changes. They went to the Copy area and thought that Copy All meant copying everything on that set. Really, now every telephone in the company that had it's own DID is a copy of one set. Bummer.
Emergency site visit, backup from E drive. Your a hero, and they're a zero. I always backup to E drive before I leave an install. Yes, you lose the hardrive you lost the backup. Then backup to some other media. This is an easy interim step that could save you.
Adversity is Opportunity