For the storage tests, we ran a bare Kingston HyperX 3k 240GB SSD through three separate benchmarks, AS SSD, ATTO, and CrystalDiskMark. The ASUS P8Z77-V PRO and Gigabyte Z77X UD3 are evenly matched in read and write speeds via a 6 GB/s SATA connection. Gigabyte's board edges out a lead over the ASUS over a 3 GB/s connection in some tests, yeilding an approximate average advantage of 4.5%. Overall, these are almost identical, but it's nice to see a bit of added value with the P8Z77-V Pro's ASMedia controller, giving performance almost exactly between the 3GB/s and 6GB/s ports. This is especially valuable to those who have more than 2 SSDs, which may be a stark minority right now, but with the way SSD prices have been plummeting, it won't be for much longer.
For the USB tests, CrystalDiskMark was used to measure the transfer speeds to the Kingston HyperX 3K 240GB SSD using a direct SATA to USB 3.0 boost cable. USB 2.0 performance is a draw between the two boards, while non-boosted USB 3.0 performance falls to the Gigabyte Z77X UD3, which does not have a USB 3.0 boost option. Under the influence of Intel Turbo (using the Intel USB 3.0 port) however, the ASUS surges ahead with a 11.8% advantage in write speeds and a staggering 40.7% improvement in read over the Gigabyte board. The UASP (available with the ASMedia controller) USB 3.0 Boost mode also offers a significant boost in performance. The crazy-fast USB 3.0 speeds will be a godsend for anyone who does large transfers on a regular basis.
ATTO was used to verify that the SSD speed peaks where we'd anticipate it to. The ATTO results for Intel Turbo boost is shown above, and we still see staggeringly-awesome 425MB/s read and 410MB/s write speeds... you are able to make use of the full potential of an external SSD drive, for all intensive purposes. You do lose 20% of the performance, but for many tasks that take milliseconds to perform on an SSD, you won't notice a difference. The bandwidth is plenty good to make full use of the available bandwidth of a USB 3.0-equipped hard drive as well.