The bigger the drive, the bigger the back you need to have for when (not if) it fails.
Second hand drives I would only use for data/content I am prepared to lose. In my (anecdotal) experience I have had nothing but trouble with refurbished stuff. Not worth the few bucks shaved of the purchase price. Maybe that has something to do with this part of the world. I am certain that the South American continent gets the rejects from the production lines for the (Western) European/US markets.