Answer:
Mac OS X.
Why?
First off, we have to consider our options. The major players are:
Windows, Mac OS, and Linux/Unix
Mac OS is the best because:
- Support for automation (Automator/AppleScript) which is essential
- Better hardware all-around
- Nice functional GUI (comparable to Windows)
- Ability to run all major OS via virtualization
- UNIX root
- Tools support is not bad (Xcode)
In essence, Mac OS is like Windows + Linux/Unix.