SSD MacBook Air to LaCie Thunderbolt HD Slow Transfers

[tcsdoc]

I know this is mixing apples and oranges but I used Finder to copy my Documents folder (containing 2066 files in 28.86GBs) to my LaCie drive in just over 3 minutes, yielding around 160MBs per second transfer rate.
I erased the LaCie drive and used SuperDuper to copy my Macintosh HD to the LaCie drive (SmartUpdate). I did not check permissions. SuperDuper reported copying 449206 files with an effective transfer rate of 59 MBs per second (varied thru copying process starting out reporting 20MBs then reaching 63MBs at the end).

Any idea where the overhead is coming from for such a wide disparage in results?