From what I've read, Macs are better for graphics. Not because they get a special version of Photoshop, but because the operating system has a better design and implementation of those features that are important to graphics software. The same goes for music and multimedia software.
This might have been true a while back but as far as music production goes, this is no longer the case. It may be easier to initially set up a mac with a new pro audio card but as far as performance and stability, Macs and PC are pretty much the same. I've worked in studios with mac setups and studios with PC setups and I've seen both run smooth and crash enough to ruin a couple days of production. Now the issue may be that software makers support macs better for other reasons, such as the smaller piracy market (I know for a fact that some music software maker decided to drop the PC platform altogether because of that), or a larger already established 'pro' customer base, but this has nothing to do with inherent mac or pc capability.
UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things. -- Doug Gwyn