Mainly the price?! ^^
Once supplier Digitec (78.60CHF) itself, once supplier JACOB (144.24CHF).
With the EU version you get the Swiss power supply with Ethernet connection and 4K streaming.
Otherwise, either ask Google directly for the differences based on the manufacturer number, or Digitec Support should take care of it for you. But as I see it, Jacob is simply asking too much :P
Google officially lists the following version differences:
US / EU / JP - Outer dimensions: 121.5mm x 126.5mm x 66.5mm
UK / IE / AU / NZ - Outer dimensions: 121.5mm x 126.5mm x 80.2mm
