It's like this. RMA problems: every one in 5 asus bad rmas gigabyte has a problem.
PROOF!
Asus is one of the best motherboard manufacturers on the face of the planet. Their RMA service gets a bad rap sure. But so does any company in existance when you look at it. A hell of a lot more people speak up when they get shafted than when they don't. GIgabyte support is fine. Asus puts out more boards, which means they have more problems to deal with. Assume 10% of their boards are DOA or damaged. Assume that is 1 million boards. Okay, 10% of those RMA claims end badly. That is 100,000 angry people with access to forums just like this. Says nothing for the 9 million boards that work fine for years, and the 900,000 claims that they fix just fine. 1% bad can scar the company to people like you that read some bad and not think in the big picture about it.
Second to the OP. What makes a montherboard good:
1. PCIe Lane layout.
2. Mosfet type. (do not want dpak like the extreme 4 Z77 has)
3. VRM phase count. the more phases you have, the smaller the ripple is, and the more stable your power is, thus leading to higher safe daily overclocks.
4. Front panel connector layout.
5. Heatsink design.
6. Distance between memory DIMMs and the CPU slot. Too close and you are forced to either water cool, or use low profile memory.
7. Other features, like Intel Lan, Wifi included, SAS compatibility, PCIe lane spliters like NF200, and branded audio chips.