I only have experience with Gnome out of the two but I haven’t had the urge to switch yet. I like the look of it (I like that it looks different to Windows), the simplicity and the customisation with extensions (only a few and small ones, I recently started using OpenBar for some customization but I could do without). I keep my system rather minimal and I am not looking to put a lot of time into theming or customization.
I also tried Cosmic and I like the tiling aspect of it, but I also don’t feel the need to switch. Maybe once it is released and I can figure out how to install it on Aeon.
I switched to Commit Mono for Terminal not too long ago but I really like it. Otherwise I use Cantarell but only because it is default and I never felt the need to change it.