linux ubuntu. fedora is ok, but ubuntu rocks.
wine can run many windows applications, but not all (there's a compatibility list on the site).
if you run linux, you will avoid internet explorer, the worst browser ever shipped (you should install e.g. firefox on windows, even in the case you decide to keep windows, and "trash" virtually IE).
you don't need microsoft office suite on windows, since there's openoffice, so you don't need them on linux too
(and rememeber, if you do not want compatibility issues also with other versions of microsoft office, do not use docx and other -x formats of the last ms office suite)
for the "etc" programs, you can check wine
http://www.winehq.org/
if you will try ubuntu, maybe you can read
https://wiki.ubuntu.com/Wine
security is surely better on "linux" systems than windows system (no matter how may and good spywares, antivirus and so on you install for windows...). about speed, maybe linux will go faster, but a clean windows won't run so slower