With the various technologies supporting different approaches to the exciting 3-D printing space, which horse should investors bet on? In this video, Motley Fool industrials analyst Blake Bos takes an in-depth look at the technology behind 3-D printing company ExOne (XONE), called binder jetting. He tells investors that while this is an older technology, it has some key advantages and can be used more flexibly than some of the newer methods. He also discusses what will be key to watch as the ExOne story plays out, and whether or not he's a buyer today.