I guess the Aorus Gaming Ultra has issues with the VRM overheating so you may want to consider the Asrock.
https://www.reddit.com/r/intel/comments/7aa2og/gigabyte_z370_ultra_gaming_motherboards_with_vrm/
Almost similar. The ASRock board looks better due to more CPU power phases... https://us.hardware.info/comparisontable/3452935/geen_username/motherboards-comparison-table-1
So basically the same I’ll just pick one if they go on sale