The z77 has pci-e 3.0 and is ivy bridge ready; some z68's require a bios flash before running the ivy bridge, though I've never tested one. Both are about the same price, so unless you're getting a used or closeout special, go with the z77.
but PCi 3.0 and PCi2.0, you cant feel the diffrent anyway? can you. i'v heard that, its only on multiple monitprs ore Quad - SLI configurations you can feel it. and what about my second Question is it save to run Sandy bridge on Z77 ? and is it Easy.