You can do the same overclock with the Afterburner software that comes standard on the Hawk. The Hawk advertises 17 degrees cooler than reference and the II advertises 20 degrees cooler.....I'm guessing because they aren't as OCed as the Hawk. Here's a link demonstrating the easy of OCing the non Hawk http://www.bit-tech.net/hardware/graphics/2011/01/27/ms... Here's the website to compare them all. They're all the same hardware (other than the fan on the Hawk) with different levels of overclocking. All of which you can easily do with Afterburner software that is free to download from MSI.
The Hawk and the Twin Frozr don't use the same hardware. The Hawk has heavy duty components and nine phase power compared to four (I think) phase on the Twin Frozr and other standard 560 Ti's. The Hawk is the way to go if you plan on serious OC of your card. 1050-1100MHz is easy to achieve with these cards where as most 560 Ti's will do around 1000MHz at max voltage. This pretty much means that the Hawk will perform on par with a GTX 570.
quote from the article: "Compared to its existing N560GTX-Ti Twin Frozr II video card, MSI says that the N560GTX-Ti Hawk has more PWM modules, a better fan, a higher clock rate, better components, and achieves greater efficiency in its power supply."