I was going to compare the packages actually installed on my server, but instead just looked in the ISOs.
From memory
ls -1trR * from the e-smith directory (after mounting each ISO)
Then I used
ExamDiff (ExamDiff is a freeware Windows tool for visual file comparison) to check which files were different. This can also export the unix diff.
At work I use BeyondCompare but at home prefer free software.
To find out the changelog information was down to rpm -q --changelog -p <whichever RPM>
For information on why the packages changed see the DevInfo mailing list archives, Shad has recently commented on the changes.