Anyone can research the differences between the various drives online. For example, Tom's Hardware is a source of good information. The green drives use less power, hence produce less heat, which is important considering that Aurender puts the drives inside enclosures for sound deadening. The green drives also spin down when they can, which reduces wear. Much of the time the hard drives are not running because the SSD holds the music in the playlist. Certainly Aurender considered all of these points when selecting the green drives. Keep in mind that in the 3 or 4 years they have been shipping their music servers, they have seen no hard drive failures. None.
Even if the two year warranty is over I would not want to risk hardware failure and the distinct possibility that the manufacturer would refuse to service the modified unit, all for the sake of saving on the cost of a hard drive. The expression "penny wise and pound foolish" may well apply. Audiophilelp, if you really need a 2TB drive for general purposes, go online and buy one, they're well under $100.
Adam, if you are still a reviewer, I am surprised you would recommend such a thing.