The Asus motherboard has:Otherwise I assume the Asus motherboard is somewhat better suited for overclocking as it has larger heatsinks on the parts around the CPU socket and I assume a larger VRM power phase count, but that last detail is something that motherboard manufacturers don't always reveal and is subject to some marketing gimmicks. The Asus motherboard is positioned as a midrange model while that Gigabyte model is more of a lower-middle range motherboard.
- a higher end audio chipset (ALC1150 VS ALC887, the former is newer and modified to include an amplifier)
- support for displayport output (not a big deal if you're using the GTX 970 instead of integrated graphics)
- better LAN chipset (Intel I219V vs Realtek, Intel is thought to be more reliable)
- supports SLI and crossfire while the Gigabyte model only supports crossfire (crossfire is 2 or more AMD graphics cards running together, SLI is the Nvidia version, this feature probably doesn't matter to you)
- support for USB 3.1 and USB type C that the Gigabyte model doesn't have
In either case, I don't think I would recommend either motherboard, they have poor average user review scores (at least at North American retailer websites). My go-to Z170 motherboard recommendation is the Gigabyte GA-Z170XP-SLI ($268 NZD), it's a midrange model similar to the Asus model and costs a bit less but seems to have far more positive reviews.
Thanks for the details and the recommendation! I think I will go with the Gigabyte-Z170XP-SLI then.