There's 3 kinds of cards. Reference, consumer, enthusiast. Reference is basically the exact same thing as what amd/nvidia puts out, has the same pcb, same clocks etc. Consumer is AIB partner cards, they'll have better cooling (mostly), some have custom pcbs and a slight OC on the clocks. Msi Armor is a consumer card. Enthusiast cards are high end, best cooling, all custom pcbs, designed with high OC and high potential user OC. The Msi GamingX is an enthusiast card.
Biggest difference is price. While benchmarks will show enthusiast being better than consumer grade, it's a gimmick really. A 1070 enthusiast card might see 10fps more than a reference 1070, they still fall into the 1070 range. Even a 1070ti reference still gets better fps than a 1070 enthusiast card.
So unless you like the looks of the GamingX better, the Armor is really just as good, the 5fps or so doesn't really affect much. Most ppl don't push OC on their gpus further than any software settings, about 108% anyways, so paying extra for enthusiast grade cards is pointless for most ppl. Your decision.