Microsoft's servers are definitely part of it. I work for a county government and when we run updates on a new or imaged Windows 7 install, the download takes much longer than you would expect for say 60MB of updates.
Whereas, I get 3 or 4MB/s when I do Ubuntu updates.
Good question OP. I've wondered about this myself.
AMD FX-8120. 8GB DDR3 1866. Ubuntu 12.04 64bit
Computing is fun again.
That's why I disabled the automatic updates when I was using Windows.
"The difference between Linux and Windows is that with Linux you're in the driver's seat, but with Windows, Microsoft is driving...and you're tied up and locked in the trunk."