CPU tests when used for motherbaord comparison are more for validation than actual performance analysis. Since these tests are based almost entirely on the CPU and memory themselves rather than the motherboard, we ran the tests just to be sure all of the parts cooperated. As expected, the results for each board are very similar, with the Gigabyte just barely edging out the ASUS (an insignificant increase) due to a slightly higher default frequency, which we've often seen Gigabyte boards doing. We can see the minor performance increase the use of XMP gives us on each board. It is hard to judge how a motherboard performs on paper in real world situations because by definition, these situations use several components rather than relying solely on the motherboard. The PCMark benchmark uses real-world tests to provide a score of overall system performance. PCMark7 shows an increase in overall system performance offered by the XMP profile setting, but it is relatively small.
The ASUS P8Z77-V PRO and Gigabyte Z77X-UD3H see nearly identical performance across the board in stock configuration and with XMP enabled. The Gigabyte does hold a very slight lead in copy and write speeds in the stock configuration, although the XMP clock was 33MHz higher than the ASUS board, at 3.833GHz. Again, this is more of a validation, and both boards hold up, and we see a nice jump in RAM performance (particularly read) with XMP enabled.