While I was talking to 3Ware about this exact product back in February... It was stated to me that these cards are the same exact set of chipsets except they are the faster versions... Plus they have a better version of managment firmware and they finally have a good linux manager...
The firmware improvements and manager will end up in the older flashable cards... and the mgmt sftware will be usable.
Now, as far as there being cache... he never mentionsed that and actually said that the improvements are on the 12 drive capacity... and the faster processor.