As others have stated from a game artist's perspective, the only worthwhile reason to get a Mac is to be able to publish to Apple's app store. Unless you fancy yourself as a indie developer targeting iOS and a artist then there's no reason to do that.
How old is your current pc? If you bought it recently it most likely is a waste, if your pc is ancient and due for a complete replacement, then it might be a good point getting a mac, if you're really aware of what you're doing, with the full knowledge that a mac will not give you a upper hand compared to if you had owned…
Always some guy who thinks it is sacrilegious to talk about the merits of a Mac vs a PC in a thread discussing the merits of a Mac vs a PC. I mean, the OP wants to know how a Mac would compare to his PC, isn't that the whole point of the thread? How do you not compare it to Windows, what should we compare it to, a dead…