Monitors have really good color science in its display. But standing today, I would say it is more of an inclination for Mac which makes apple users say that to avoid what we call in marketing post-purchase dissonance. PC provides a lot of flexibilities to you in terms of upgrading/ customizing your setup which can become very costly in a Mac. If you are willing to use Final Cut Pro X for color grading then Mac will be the choice since it is not available for windows. Adobe premiere pro runs on both and is also widely used for color grading. One of the other popular softwares is Da Vinci Resolve. It is supported by both Windows and Mac.