rsync is an advanced tool to synchronize remote directories. You can get it for Linux and Windows (probably also for Mac and further OSs), but it is a command line tool.
Here some instructions and tips how to rsync the TeXLive repository so you can set up an own HTTP or FTP server as repository for you local TeXLive.
A general description on how to rsync TeXLive can be found at http://www.tug.org/texlive/acquire-mirror.html, but I most likely read that page already.
For Windows there is e.g. cwRsync which is based on cygwin, a Unix emulation for Windows.
Another Windows HowTo to install and setup rsync can be found at http://optics.ph.unimelb.edu.au/help/rsync/rsync_pc1.html. This is useful if you want to update your copy of the TeXLive repository automatically.
To synchronize it simply use the following command line, where %CTANMIRROR% is a rsync CTAN mirror:
rsync -a --delete rsync://%CTANMIRROR%/systems/texlive/tlnet/ "/cygdrive/<driveletter>/dir/subdir"
So e.g., to sync from DANTE's rsync server to C:\texlive\ use:
rsync -a --delete rsync://rsync.dante.ctan.org/CTAN/systems/texlive/tlnet/ "/cygdrive/c/texlive/"
Here -a stands for archive mode (you might get some warnings that Unix/Linux permissions can't be set; that's normal and not really an issue) and --delete will delete all extraneous files (in the local destination) which do not exist on the remote source folders.
Best Answer
(Not meant to be a complete answer, just an addition to others.)
TeX Live provides more secure defaults than MiKTeX and probably pays more attention to security in general. For example, section 3 of this paper describes a simple way to make document (or bibtex database, or package) viruses which would almost make MS-Word look as secure alternative ;-) This attack doesn't work with TeX Live's default settings, regardless of the platform (Windows or other).
Not completely unrelated, TeX Live is designed to support multi-user systems, including being installed on a servers and used on network clients, possibly with mixed architectures and OSes. (Which may be totally irrelevant to the OP, but mentioned only for information.)