If that's all there was to it, it would be an easy decision. You keep talking as if Apple finally getting OS X right and being cheaper, for the moment at least, is all you should need to know to start tearing out your existing infrastructure. I've seen lots of companies come out with a product that's "the next big thing" that's going to unseat all their competition. So far they have a history of being able to build one good, enterprise class OS, and priced it cheaper than Microsoft. You ask too much on that alone.
I thought businesses were in it for the money. If it costs less and does the same thing or better while being as safe or safer, you use it. Works for table saws and IT infrastructures. As I said, the only question is the expense of the switch, not so bad for table saws, kind of expensive for IT infrastructures.
Anything else is a waste of money, be it because the PHB was mesmerized by the MS rep or the head of IT is worried about the size of his kingdom