Both are 8GB (4GBx2) 1.5v. The Crucial has 8-8-8-24 timing at 1600 vs the Corsair at 9-9-9-24 at 1333 (whatever that means...all I know is that lower is better). Additionally, the description on the Corsair says that it has heat spreaders, but I don't necessarily read the same thing on the Crucial. The Crucial has holes on the top for "better airflow" and I don't know if that's true or a gimmick.
Currently I am not OC'ing an i7-2600k, but I may in the future. My system is air cooled and has a CM Hyper+. I am currently using the Corsair, but if the Crucial is significantly faster, I will use that one and give my Corsair to another i3 build in the house.