I have the CECHK01 model and though starting with this model there are only 2 usb ports and NO memory card slot (i.e. i think this is because this model onward is not backward compatible so there's no need for the memory card slot to load ps2/1 game settings); the cell engine is a newer version which is reportedly better, performance wise, and runs quieter and cooler (i.e. the latter 2 features are great when watching blu ray movies :2thumbsupthan earlier iterations other than consuming less power (i.e. if i'm not mistaken now only 135 watts down from 200 watts).
i also believe that latter versions have the new dualshock controllers, which were upgraded from the original six-axis controller.
the hard drive is not really important, whether you have only 40, 60, 80 or 160GB. this is because you can easily upgrade the drive with a 3rd party hard drive (e.g. 1 TB!!!:whoa.
i'm not sure if the model versions are the same globally but you may want to check out this site for ps3 bought in other regions: