I'd say Mac. Macs can run any OS without violating EULAs anyways (OS-X, Linux, Windows)..
Have you seen how much Windows Vista costs?!?Mac cost a lot, whereas on for windows is much cheeper, So i prefer Windows.
Nowadays I use Windows XP, I've tried Linux but it's ugly and hard to use. I'm thinking to buy a Mac, but i've a new laptop (1 year) and i've no money to buy a mac...
No offense, but I don't care how pretty it looks, how user-friendly it is (if it's complicated, I WILL figure it out), or how 'easy' it is. I don't spend the majority of my time browsing the web, using PhotoShop, or typing essays. I'm a PC gamer, a game/mod developer/programmer, and an ethical hacker (even though I could do that with a Palm Pilot). Windows fits all of those, Linux fits some of those, Mac hardly meets my requirements.
Linux is not ugly or hard to use... have you looked at it lately? You can changed your window manager and themes easily if you don't like the defautl... Look at the ubuntu distro... easiest ever to install, easier to use than windows, easier to install software than windows ...