You know me, I don't do straight fwd simple answers.

In windows; ie8 because it handles my dev tools, PAC files, and local proxies better/more. Also, IMO it's not any more vulnerable to exploitation than any other connectable, especially when using safe practices.
In nix at home; it's FF but I generally don't do much browsing in nix because what work I do there with the desktop is done on 802.1.1 thru WinVNC using an SSH tunnel(basically a VPN...makes all transfer encrypted...safer even when going thru a NAT box)...usually don't do much with the nix desktops anyway as I'm not really the clicker/GUI type when I have a reasonable choice.
Sorry, in addition to wanting to explain my answers, I also wanted to brag on my home rack network setup a bit.
