This is taken from TechPowerUp:
"The Gaming X features double ball bearing fans, a few gamer-specific features though MSI Gaming Control Center, a back-plate, and a significant factory OC. The Gaming Z, on the other hand, gives you all the features of the Gaming X, but higher clock speeds, and a custom RGB LED setup lining the top logo and an MSI "Dragon" logo on the back-plate."
So basically, if you like flashing lights get the Gaming Z. As for the higher clock speed, you'll be able to overclock the X to match the Z with ease. So you're really only paying the extra for flashing lights
