Benchmarks: storage
MSI's Z97 motherboards both seemed to enable UASP by default with impressive out-of-the-box read and write performance with an external SSD. The ASUS Z97 Pro Gamer toggles UASP off for its default setting allowing the user to turn it on with the press of a button. With UASP enabled all boards converge on virtually identical performance.
SATA storage speed is determined by the Z97 chipset so performance should be identical between Z97 boards, which it is. Third-party controllers, such as the ASMedia ASM1061 chip used by the MSI Z97 MPower, are a sizeable chunk slower but still deliver enough bandwidth to let SSDs stretch their legs.
M.2 is also provided by Intel's Z97 chipset and all the tested motherboards made use of the same 10Gbps revision of the M.2 standard, hence the similar results. Some vendors are implementing the 32Gbps Ultra M.2 standard but this is typically reserved for flagship motherboards. Improved PCIe storage is expected to be one of the hallmarks of the next-gen Skylake 100-Series chipset.