GoodNotes recently fixed the Cloud sync, and I'm thrilled to use it again at full power on all my devices.
This sync problem made me seriously consider a switch to Notability.
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To my personal taste, the UI is more refined than the one from Notability. Although I like the home screen / file manager in Notability a wee better than the bookshelf in GoodNotes.
It's hard to explain, but the writing scale in Notability feels a bit unnatural to me. In GoodNotes I have a 1:1 experience, in Notability I don't.
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And finally, the customization of templates in GoodNotes. I've made a ton (see my YouTube channel), and I like how you can use several templates in one notebook.