technical differences between the different mac os released?

hi
i would like the know the the different enhancements that have occured from mac os 8.5 till date. i would appreciate if anyone could guide me to the source documents which will satisfy my query.
in short i would like the track the technical( operating system point of view i.e low level details) differences between these
diff os?

http://www.theapplemuseum.com/index.php?id=tam&page=software&subpage=macos

http://www.macos.utah.edu/Documentation/MacOSXClasses/macosxone/macintosh.html

http://www.fact-index.com/m/ma/mac_os_history.html

And the excruciatingly detailed http://www.kernelthread.com/mac/oshistory/

The main difference is that OS X makes the quantum leap to Unix (freeBSD/Nextstep) which puts this OS to the lead of even Linux