Linux or Windows
To throw my .02$ into this fray I say:
Linux is for work and Windows is for play :)
But seriously I have been amazing at how many free tools Linux includes with the OS (or via the net/repos) for free.
Then there is the issue of the constantly evolving Windows “shell” which keeps changing commands almost every major release of the OS. With Linux I can run basically the same command,with little or no changes, that I ran almost 15 years ago when I started playing around the OS. If Windows did this I would have much more respect for them and their OS.