Basically its is the stepping used for the cpu (timings) from what little is out there about it, the e5 stepping venice core is more desireable, some report that the sssms (e6 stepping) venice core has issues running 1T timings with some memory, and when OC'd...look here for a description of what cpu stepping is :
http://www.techpowerup.com/articles/overclocking/29