Intel would probably rather you compare Z77 with xyz67, that being if they produce a x78 chipset.
The x6x series was a bit messy, but the latter released Z68 gen3 mobos are pretty damn good. They both require the IvyBridge cpu to use PCIE3, otherwize with a Sandy it'll be PCIE2 - in the add-in card sense, i.e. graphics. Whether the Z77 sports the PCIE3 "high speed data link" for harddrives only, ala the x79, I don't know.
Personally I'm advising clients with quality latter Z68 model mobos to keep them.