Buying a processor. What’s the difference between OEM and Retail?

Hello All,

What’s the difference between OEM and Retail? Does it really matter for buying an i7 processor?

The reason that I ask is because I am going to buy an i7 processor for the gaming system I am building. I am considering one of two processors. One processor is the

i7 – 950 3.06 GHz: cost: $569.99 - RETAIL

and the other processor is the

i7 – 960 3.2 GHz: cost: $574.99 – OEM

For the extra $5.00, I would prefer to have the extra Ghz. Is there a big difference? Does it really matter which one I buy?

Thanks,
Jim