Bringing up both boards on Newegg and comparing...
1) They're both Micro-ATX
2) RAM specifications are the same (4 slots, 64GB max)
3) You'll use a dedicated GPU so onboard graphics outputs don't matter
4) They both have a PCIe 3.0 x4 M.2 port
5) They both have 6 SATA3 ports
6) They both have a PCIe x16 + PCIe x4 slot combination
7) They both have the ALC887 sound chip
8) They both have 2 PCIe x1 slots
9) They both offer RAD0/1/5/10
They're effectively the same thing and most H170 boards at $90 are essentially the same thing.
Here's how they differ:
1) Gigabyte has 4 USB 3.0 ports on the rear, Asus has 2 ports
2) Gigabyte has a Realtek GbE Ethernet port, while Asus has the Intel V219 GbE
For the same price... choose the brand you like better, they're essentially the same board.
When you're comparing boards you need to go into it knowing what features you absolutely need. If you need RAID5 on board, then you can eliminate anything without RAID5. If you want to run a GPU and a PCIe x8 RAID controller then you need a second PCIe x8 or x16 slot with an electrical x8 connection (or x16) - that would eliminate both boards as the second slot is electrically x4. 99% of builds these days are 2 RAM modules, SSD, HDD, and a GPU. Literally every board supports that.
Here the only difference is two USB 3.0 ports and which GbE controller it uses. If you'd use a WiFi card anyways, you don't care about the LAN to start with.
Personally I like Asus better, but Newegg has a better price on the Gigabyte. If you're outside the US, you'll have to go with your local prices but I can tell you in the US the Asus is typically more expensive which may - or may not - indicate a better build quality.