Originally Posted by
acheter
Aero - one blower fan, always spins, loudest, highest temperature, not overclocked, little overclocking headroom due to heat. Basically the same as the Founders Edition at a lower price.
Armor - typical MSI two fan design, fans are off when idle and only turn on when gaming, much quieter, lower temperatures, not overclocked.
Armor OC - exactly the same as Armor but factory overclocked.
Gaming - better two fan design, fans are off when idle and only turn on when gaming, quieter still, even lower temperatures, factory overclocked.
Gaming X - exactly the same as Gaming but with higher factory overclock.
In theory, the Gaming X would have the highest possible overclock, followed by the Gaming and Armor. In practice, they'll all overclock to roughly the same place, and the Armor may just run slightly hotter / louder (1-2 degrees, and 1-2 dB respectively).
I would avoid the Aero / Founders Edition and go with whichever of the Armor / Gaming cards comes out to be cheapest.