I clicked Linux despite using Windows for more time because I only use Windows for non-relevant stuff (gaming mostly, also studying chess since good software only exists in this platform, sadly...). For research/programming/reverse engineering/security/important work I use Linux, specially Debian GNU/Linux or based distro (except Ubuntu), but I guess any open-source OS will do fine as well (FreeBSD and OpenSolaris did very well last time I tried them).