I still prefer OS X to Windows 7, but the gap has closed up quite a bit and I couldn't guarantee that the cause for my preference doesn't ultimately boil down to it just being that I use one for play and the other for work.

I think that anyone could make a strong argument for why they subjectively believe that one or the other is objectively superior. But I long ago gave up on encouraging friends & family to try Macs. It's not worth the irritation of learning a new OS for them. For the Windows things I do still fret about like removing crapware and installing proper antivirus software, it's much easier for everyone involved if I just arm-twist them into letting me make sure everything's set up properly.