Our CPU tests are less of a comparative benchmark but more of a general validation. We don't expect to see much, if any difference. And significant differences (>3%) signify a significant design flaw. We see nearly-identical performance, which we expect, and doesn't indicate that either board has any significant comparative design flaws.
The ASUS P8Z77-V PRO and Gigabyte Z77X UD3 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 with XMP enabled.