There's really no difference between the Gaming and the Gaming X, other than a boost in core clock speeds. The Gaming model has an already factory overclocked base clock of 1632Mhz in OC mode, while the Gaming X has a 1708 Mhz base clock in OC mode. So if you're going to overclock it anyway, don't get the Gaming X as you can save a little lunch money, and you'll still get the same overclocking potential as the Gaming.
It's entirely up to you tho, if you want to get the Gaming X version, by all means, do so.