Radeon 7770: OC or Stock?

Hi, I was looking to get a Radeon 7770 for my comp, and I know there are multiple brands out with there own versions and styles. I was wondering, how much of a difference is it between something that's pre-overclocked (like the Sapphire HD 7770 OC) and something that's "stock" (like the HIS iCooler 7770)? I'm seeing a few small stat changes but is it really worth it? I know Sapphire is a good brand and i was leaning towards that card in particular, but wanted some feedback first