If I had to pick between the two (I picked ASRock for my Intel build, sorry!), I'd go with Asus for the best-in-class UEFI and DTS encoding support. I'd expect them to be roughly equal in just about everything else.
Canon 6D|24-105/4L IS USM|70-300/4-5.6 IS USM|40/2.8 STM|50/1.4 USM|85/1.8 USM|Samyang/Bower 14/2.8 Full-Manual Rectilinear Wide-angle|24/2.8 IS USM|
Canon EOS-M|11-22/4-5.6 IS STM|22/2 STM|EF-M 18-55/3.5-5.6 IS STM|