The OEM (bulk) Radeons are clocked slower at 163/163, than the retail Radeons which run at 183/183. Also, the OEM Radeons normaly have slower ram which limits the ability to overclock it. Many people with OEM Radeons have gotten them overclocked to the Retail speed, but its not a sure thing. So I would suggest you get the retail, unless you can find the OEM a whole lot cheaper.