I use Windows 7, Ubuntu, Centos and Fedora.
From a pure install to fully patched instance, windows typically takes longer than linux but there is more to it than it seems.
My windows media is "as of purchase date"
My Linux distros are always "latest production snapshot from vendor"
If my windows media is 2 years old, it has to pull 2 years worth of patches. Last time I purchased media from microsoft, the iso had most of the recent patches bundled in and it didn't take long to patch.
I can't remember the last time I stored a Linux iso. Every time I install a linux instance, I get the iso from the web.
The key thing for me is install to final, fully configured ready to use.
A barebones linux or windows install is useless.