I can't comment on my experience with either of those two mobos, but my experience with ASRock and MSI mobos has been good with both OEMs. I preferred ASRock for my Z77 builds but I think that MSI Gaming mobos are very interesting on the Z97 platform.
Overclocking is a very hit or miss proposition. With two mobos of the same model you can get different results, and the same is true of the CPU. "Identical" processors don't always OC the same.