Good for Gigabyte
I just recently found out I'm a GB fanboy. I've owned the following from them:
The only RMA's that I've had with them were on the EX58-UD4P board and it arrived with bent pins... could have been Newegg's fault. I also killed my first OC board but that was my fault (I think). I told them what happened and they still RMA'd it for me
For MSI, I've only owned the Z77A-GD65. While I liked how the BIOS was organized and how well it worked, it did decide to give one of my 3770K's 2.2V randomly. A few of the phases went up in flames and it killed them chip also.
With Asus I've owned a Rampage III Extreme and a Maximus IV Gene Z. While the RIIIE was an incredible overclocker, it had many intermittent issues (had to put additional pressure on CPU Heatsink to get it to boot sometimes, sometimes it would boot without sound, etc.). I ended up RMA'ing it and selling the replacement for my X58A-OC.
I've only owned one ASRock board too, the Z77 OC Formula. I liked it for the month or so that I had it but sold it in favor of my UP7.
With almost all good experiences with Gigabyte, you better believe I'll be leaning towards them on Z87.