We don't know the full specs of each gpu brand yet, but in previous series, gaming X had better VRM for higher overclocking abilities, higher default memory clocks and slightly more sophisticated cooling for lower temps. As well as dead silent fans. Im always running my fans on 60% to have low temps and I cannot hear them at all.
Maybe no huge difference to Duke, but sound level, cooling and good VRM for OC is quite important to me. I could go above 2050Mhz boost on the 1080Ti gaming X while my friends Gigabyte could not reach 2000 without glitches and crashes.
Not saying Gigabyte is worse than MSI, but in terms of the 3 aspects mentioned above, u usually get what you pay for.