My vote, Z68
Here is a side-by-side comparision.http://www.newegg.com/Product/Productcompare.aspx?Submit=ENE&N=100007627%2050001314%20600093976&IsNodeId=1&bop=And&CompareItemList=280%7C13-128-478%5E13-128-478-TS%2C13-128-506%5E13-128-506-TS
One biggy form is 4 sata 6 internal connection, only 2 on P67. The Z68 has the ability to display without a dedicated GPU (ie say your Graphic card goes out, can still use computer until replacement). Pci-e slots are diff, your choice.
CPU. Both MB provide for Overclocking the CPU, and SB processors over clock very easy, BUT you need the "k" cpu to OC. recommend either the i5-2500k, or I7-2600k CPU.; even if you don't plan on OC, you might change your mind and regreat the non-k CPU.