While Adobe dragged their proverbial asses on native system support for the Mac/iOS Pixelmator was one of the first to use native core OS integration on the Mac and iOS. Or even Inkscape for Illustrators if you're planning on ditching the Adobe blood-sucking machine.
The fact that you can even mention it while leaving out a great app such as Pixelmator/Pixelmator Pro shows a lack of hands on research.
GIMP is just outright crappy, unless you like the feel of UNIX X Window system built apps or old style Windows Apps. It's usually my go to when getting any of my artist buddy's in to the fold. ProCreate is a great app for sure, and especially for the price and feel for a traditionally trained artist.
