user site-packages, --prefix, --home and friends

[Carl]

I am very confused by PEP-370 per-user site-packages. It is not
mentioned at all in the document about installing Python modules :
http://docs.python.org/3.0/install/index.html.

It seems that --home or --prefix already provide per-user site-
packages capability. Can someone explain what are the differences and
what is the best practice in various situations?

Thanks, Carl