I ran this exact same thread about 2 weeks ago. Everyone agreed that MAC sucked.
And corpsie, I disagree. Audio and video used to be better, but I don't think it's superior anymore.
I know of a few fx houses her in LA that have switched from MAC to PC because the software ran exactly the same if not better on a PC.
If the software runs the same, then you look at personal preference, such as:
ease of use, how easy is it to upgrade, layout, compatibility with other software, and maybe even the PC mouse can make a difference.
If they run the exact same, then PC seems to be the logical way to go. The wheel mouse offered by PC has cut my work time down simply because it's quicker. The fact that I can right click and bring up menus also is a huge time saver.
I also know that in FX we can run puppets on PC which we wouldn't be able to do without windows software. Controlling a puppet via PC = Thousands saved, which in turn = saings for production, which in turn guarantees us a job.
PC is better.