iOS 5.1 file size differences - updating via iTunes vs updating wirelessly via device

[Cobra Jet]

Why is there a dramatic size difference in the actual file size of the new iOS 5.1 when updating it via iTunes account vs updating via the actual device wirelessly?

What I mean is this:

To update via iTunes - the file size is showing as 803MB

To update via the device (iPhone or iPad) wirelessly w/o logging into iTunes - the file size is showing as 189MB

?????

Anyone know the answer?? The above is definitely the file sizes I am seeing as noted for ONLY the 5.1 iOS update d/l.

 

[joeyteel]

The iTunes version is the complete firmware required for a full restore. The version directly downloaded on the device is essentially just the parts of the firmware that are changed between the current installed version and the update.