The Aero edition of all msi's card is essentially the base model, it isn't factory overclocked or had anything special done to it, as well as its cooling solution usually being smaller, less efficient and slightly louder. the gaming x is generally the best value as it is factory overclocked, maintains great temperatures and is near silent, i currently use a Gaming x 1070 and it is so quiet, i never hear it.
essentially they are both great cards with very similar performance, if you have the extra few bucks for the gaming x, get it, if not get the aero, there both very good cards with attractive designs.