To test the USB 3.0 performance we have the Patriot Supersonic Magnum, the fastest USB 3.0 thumb drive that we know of. In the future, we will replace it with a 2.5' USB 3.0 SSD, but for now the Supersonic Magnum what we have. As you can see, the Z97 boards all provided similar results.
Using the RightMark Audio Analyzer, we tested the dynamic range using 24-bit/192Hz. The three Z97 boards all produced similar results.