If you don't plan on doing any overclocking and are going to use the onboard graphics, then there really isn't any meaningful difference between them apart from a pair of SATA3 ports and SSD caching (intel SRT).
If you plan to use a discrete graphics card, but still want access to the onboard graphics core (for Quick Sync) then the Z68 board is the only way to go, due to the exclusive use of Lucid Virtu.