>On the same machine, a default Windows 7 install will take 1.6GB of RAM.
Are you sure about that? https://i.imgur.com/jXRrEJS.png
My mostly stock install of Win8.1 seems to use less than 600MB at idle. I 100% agree with you that Linux can be more efficient (that screenshot was taken from a VM running on Linux, which is my primary OS), but Windows isn't that awful memory wise.