Raidiator as you know is the firmware / operating system for readynas devices. The most recent devices have a new operating system called OS6 (Operating System 6). The most noticeable difference is the appearance of the GUI, which for some is easier to use.
I think it would be easier for you to search the forums and internet and read some of the information that is available on specific issues rather than look for a list of differences. Google and the forums have plenty of information.
If you then have more specific questions users may be able to answer them here.
