From the builds I've done on the Z87, Asus seems to have the best handle on the Z87/Haswell, the BIOS's are better tuned, handle DRAM well, run cool, and tend to OC better using less voltage
From the builds I've done on the Z87, Asus seems to have the best handle on the Z87/Haswell, the BIOS's are better tuned, handle DRAM well, run cool, and tend to OC better using less voltage