1. Using the same manufacturer does make tech support easier as they can't "blame the other guy"
2. Last generation, MSI and Gigabyte were the performance leaders in the GFX arena... Gigabyte had a rather high % if extremely negative reviews (20+%) from newegg board owners ... about 3 times the competition. This round, MSI seems to be getting most of the accolades.
3. Last generation, MSI and Gigabyte were the more reliable and performance leaders and Asus had an extremely high number of highly negative newegg user reviews. ... This round, Asus has placed a number of boards at the top of the performance rankings, but also a lot at the bottom.... Gigabyte and MSI still lead in the overall reviews from board owners but again, some boards are doing very well and some not so well.
But it's more about which model, than what brand in most cases. For the GFX cards ....
MSI Gaming > Gigabyte G1 > Asys Strix > EVGA SC
For motherboards ... depends on the price category.... Below $150, most Asus boards have a substandard audio solution (ALC 892) where as the competition is offering ALC 1150.
The Gigabyte Gaming 7 is a stellar board and the MSI XPower Titanium is incredible... for Asus, my choice would be the Sabertooth