Z87 will definitely need a BIOS upgrade to run any of the Haswell processors. I made this mistake when I bought my 4690k and a Z87 motherboard and couldn't boot. I swiftly returned the Z87 and spend the extra $ for the Z97 simply so I didn't have to RMA the motherboard for an update. As far as performance, not really. The Z97 really just added the chipsets for Haswell processors. So unless you just don't want to mess with updating the BIOS, I would stick with a Z87 IMO.