Different versions?

Why goes Gamestop list a later version number than the downloads page here at Stardock for Galactic Civ Ultimate Edition?  Stardock has 2.04.017 and Gamestop has 2.04.019.  I would have thought the most recent source would come from Stardock directly (and I hate dealing with Gamestop).  Is the Gamestop version somehow specific to them but not more current?  They are different file sizes too (Gamestop's being listed as larger).

Which should I be using?  Any help is appreciated.