It used to be that Macs were the go to for graphic design and audio engineering, but really the playing field is pretty level now and it's what you feel comfortable with.
Many Win based computers can be more powerful than their Mac counterparts as there's a wider array of hardware available.
Where Macs do well is they limit your choices: you don't get to choose the hardware components, so they can write their OS to work on the specific hardware. This means that the OS is going to be a little more lightweight and agile. Also, you won't have to worry about drivers and configuration like you would with a Windows PC.
To me, it boils down to:
If you want to tinker and want more control, at the risk that you might break something, or you might have to work more to support it. Get Windows.
If you don't mind sacrificing control, for something that requires less maintenance, and just works brilliantly. Get a Mac.
