I was in the OS choice situation myself some time ago, and I ended up simply picking Windows 7, after seeing that a reasonable amout of high scores on the hardware/config list were done on Windows 7 machines.

If you have a spare USB stick lying around, BAMT Linux is sweet as well. It's super fast to set up, and the command line work is really not that difficult.

The only reason I chose Windows 7 over BAMT was comfort. I simply have more experience with Windows software than Linux software.