Erm, OK, something just to go over first.
You can't compare a Venice Core to a "retail version", any CPU core, including the Venice, is packaged as either retail or OEM. The core refers to the actual architechture of the chip, not how it's packaged.
Now, I'm assuming the retail version you are talking about is the Winchester core. The Venice core will overclock exceptionally better than the Winchester core, it has a better memory controller added to it so you can hit higher speeds with less voltage than the old Winchester. For example, a 3200+ can hit 3GHz with the right knowhow on air with a Venice core, Winchesters most likely won't do that.
The other couldn't go to 3200+ speeds without overheating. It would get to 58 degrees C at 3000+ speeds. I played around with it to see if it was the installation or the chip.
This is because companies like AMD and Intel make one chip so to speak, and test the chip to see what speeds it can run at. If a chip can't make the voltage and clock speed of say a 3500+, but can for a 3200+, they'll label it a 3200+. That being said, a core might be able to run at 3500+ speeds, but may miss the vcore requirements by like 0.1, they'll label it a 3200+ when infact it can run a lot faster than what the stock speeds are.