It really depends on which OS you prefer. I know you haven't used either, though I'm guessing you've probably used Windows 7, which gives you an idea of what 50% of Windows 8 is like. Go to a store and test out OS X and Windows 8, and see which you like best. Also consider how important a touch screen is since OS X machines lack a touch screen.
-------------------- Lisa Gade Editor in Chief, MobileTechReview