If you only care about overclocking performance, Gaming 5 will be slightly better. It has 8 true power phases which is also digitally controlled. G1 Sniper, on the other hand, has 4 true phases doubled to 8 with a doubler. It also has a hybrid/analog controller. They have exact same mosfets with exact same amounts, same inductors and caps. So they are really very close. Gaming 5 is just a bit better and efficient with its true phase count and digital controller.
But in the end, both boards have pretty much the same power output potential. They will both perform fine with some decent overclocking around 200-220W which is more than enough for a water cooled overclocking. You'll be limited by your cpu before you hit the motherboard limit.
For the memory overclocking, both boards have 1 phase memory vrm and exact same fets. It's quite enough to run a factory overclocked ram sticks. More than 1 phase memory vrm is just for LN2 overclocking.
So the difference between two board is really negligible in terms of overclocking potential.
If you care a bit more than overclocking performance and efficiency, like audio performance, then G1 Sniper offers the best solution in the market. It employs a quad core Creative Sound core 3D audio processor, so it is way better than any other boards with realtek alc1150 codec or some gimmicky stuff like Asus's SupremeFX (which is actually a renamed realtek alc1150).