My bets are on linux, you think ubuntu is hard. Try arch xD -- You build it from the terminal up.
Other then that I use Windows with a spare hard drive I have formatted just for working. (Since its my gaming PC and all)
Windows XP was good After that just sucked (Resource hogs and might as well come with Virals pre-installed.)
And Mac wishes it was linux. (Even though Mac Came first, Still wishes it was linux.)
well if you see in the market most of the people use windows thats why it became more user friendly and mac doesnt its not a issue what will happen if you take mac obviously it will take some time to undersatand o.s it also depends on your use if you are taking for regular use then go for mac but if you want it for the developing then go for the windows.