I've actually had long arguments with people who say that for any kind of graphic design, you HAVE to use a Mac. I don't believe this to be the case.
Their argument is basically based around the fact that Windows doesn't handle massive image files as easily or smoothly and that it's very unreliable.
Have these people actually tried doing so in Windows? I've got images that are multiple GBs have had no issues there. I wouldn't be surprised if "large" to them was 50MB.
I wonder how they would respond to you telling them that 3DS Max isn't available for OSX? Probably be along the lines of "It' crap anyway".