Whats the Best OS?

Depends on what your priorities are.

Windows is easy to use, has plenty of the best software and games but can't be customized easily and then there's the virus problem.
Linux has a learning curve to it, but you are free from any copyright and most viruses are built for windows so you're safe.
OSX is a balance between the 2, it's not as highly customizable as linux and then once again apple hardware lock unless you build a hackintosh


My suggestion?
Dual boot windows and any flavor of linux you like.