It could be binned which would make it worth the premium but just because it is an OC model doesn't mean it is certainly binned. In fact I doubt it is. If someone can say for certain that it is binned I would buy the OC version though. As for the BIOS... you can always answer this question for yourself by going to tech power.com/vgabios
look up the 2 bioses in question and look at the hardware ID. The sub id will be different and it will actually change the sub id reported by your card if you flash the bios.
Personally though I would not do that. I would instead recommend that you use the bios editor, up the fan profile, up the power a bit, up the voltage and leave the clock alone for the first flash. Use precision x or afterburner to find your max OC after upping the voltage then edit the bios again and up the clock a tad.