I'd recommend Mac, but since that wasn't an option I'll say Linux. Windows sucks big time. The only thing I use it for is for browser compatibility testing and ripping/burning music.
The things I really hate about Windows is:
- All the problems with viruses and have to run an anti-virus that takes up a ton of resources/memory
- Just about all software (including the O/S) is extremely bloated
- Most software is extremely expensive
- Having to find a driver for anything you plug-in is a major PITA.