One difference that I have noticed: if you have fixed the size of your swap file, then Norton will move the swap file to the beginning of the drive. This optimizes access to the swap file. Fixing the size of the swap file keeps it from becoming fragmented.
It also seems to me that Norton takes longer. I use the WinME version every day. Usually takes less than 2 minutes. Also, I only have the operating system and programs in the boot drive. Data files like MP3's are in separate partitions. I defrag data partitions once a week, or once a month, depending on file activity.