Definitely Material Design, it just looks so much more modern, clean, lightweight and consistent than GNOME. For me it’s one of the big drawbacks of using Linux.

I love GNOME for everything except FreeCAD, KiCAD, Inkscape, and to a lesser extent GIMP, when working on a 1080p 17" laptop, on Wayland. There is far too much space taken up by the window header bars and the font line spacing is useless for managing complex trees. I always feel claustrophobic with these applications. Everything else feels fantastic with GNOME. I usually use the flatpak versions of these other apps and force them to use the built in KDE version of each app with my desktop running GNOME.

I can’t stand the Gnome design. Material wins by default for me, but I do like it as well.