The bottom line is in the early days of what is now called MacOS, there were Mac graphics programs (aka "apps" or applications) which were significantly superior. And, for many years graphics departments were Mac departments because until around 2005 Macs were the best for graphics.
It's now 2018 and I do not know if MacOS is still the premier OS for graphics and/or graphics programs. So many years have passed that I would expect graphics programs for Windows, Linux and MacOS are pretty much equivalent.
Apple has pretty much switched gears, so to speak. Apple (formerly Apple Computer) is now mainly iPhone and the Apple Store content. Unfortunately, these days I do not have ready access to anyone in a major corporation's graphics department to talk to about the current state of affairs.