There is an undocumented DLL-file supplied with Notes that will do this for
you. Just add this to your notes.ini file:
Close down Notes.
Edit you notes.ini file, and add the following line at the bottom:
AddInMenus=C:\Notes\nntediff.dll
Restart Notes, select the documetn and it's conflict.
You'll get an additional menu option under Actions called Difference of 2
documents. This neat feature will display all fields that differ and their
respectively content in an dialog box for review.
Of course, since it's undocumented, don't bet on it always being available
in future versions or it's behavior remaining constant.
Warning sometimes it will crash your notes client so save all your work first!