Notability uses less storage space than GoodNotes.

GoodNotes allows you to install the app on multiple devices whereas Notability requires a separate purchase for each.

GoodNotes allows multiple people to edit the same document if they all have GoodNotes installed.

Since this is a feature you want, I would recommend Notability over GoodNotes. When you playback the audio, you will see the notes during the section they were recording.

Notability enables you to record audio and take notes together.

Since you enjoy using many brush pens and other planner pens, you might prefer the options that GoodNotes provides. There is a larger selection of pen types with more options to adjust the stroke with and pressure sensitivity.

GoodNotes offers a wide range of colors for doodling, drawing and writing.

Since you prefer each note to be a separate file then you will probably prefer Notability.

Only Notability supports Box and WebDAV so since these are backup systems that you use then this difference between the apps might be a deciding factor.

Notability journal template