Difference between Deskstar NAS V1 and V2?

I am making a purchase decision for a new hard drive and it’s leaning towards a HGST deskstar nas drive. However I noticed ther are two versions of them, V1 (HDN724040ALE640) released 2014 and V2 (HDN726040ALE614) released 2017. What are the differences between these drives? The only difference I can tell from the spec sheet is that V2 has twice the cache, or are there any improvements made that you can’t tell from the spec sheet?