Results: 3DMark and PCMark
Because Intel’s integrated controllers and closely-regulated firmware removes variability between platforms, any sizable difference in the benchmarks should be attributed to either broken settings (like bad memory timings) or unintended overclocking (cheating). Smaller difference can be caused by acceptable differences in base clock (99.8 to 100.2 MHz, for example) or by chance, since differences up to 1% can occur between consecutive runs on the same hardware.
We started to notice a performance advantage favoring Gigabyte’s Z97X-UD5H in 3DMark 11, but the issue really stood out in 3DMark Professional. A quick run through the firmware settings proved there was no way to disable firmware "enhancement" of Intel's Turbo Boost ratios. In this case, the "enhanced" mode forces the CPU's maximum-specified ratio, regardless of the number of cores utilized in the benchmark.
Gigabyte retains a lead through PCMark, though the amount of gain is questionable since this metric is very dependent on storage performance.