One of the big reasons people like SVG is the support for multiple layers representing multiple pen colors, and most tools dealing with SVG support this. In Gcode that would require two separate files and running each separately. Axidraw will pause between layers to allow a pen swap then continue plotting.

SVG also has groups which allows for the path optimization to only optimize within groups so the group is plotted at the same time.

SVG is easy to export from Processing and other libraries. Not sure how easy Gcode is to create and export comparatively.

I’m just getting started on this path so that’s all I know of. I tried the Gcode route with an Eleksmaker A3 before getting an Axidraw and comparatively the AxiDraw and the tooling Just Works whereas it felt like I was fighting the Eleksmaker to do what I wanted.