I am system administrator + programmer and I work with different systems like FreeBSD, Ubuntu, Windows and so on. With my experience I can say that for mining the best OS is Windows as it has all needed stable video drivers, many manuals are written exactly for Windows and setup is faster and more user friendly, stability is the same as on unix. Unix is more likely for geeks that want to make a huge setup of customs and don't want to pay for Windows license, thats the difference.