The philosophies of the two DEs are diametrically opposed. For example KDE will let you customize everything, they’d even let you customize their mothers of they could, while GNOME won’t let you customize anything, at least not without extensions that break every time GNOME updates.
KDE devs are also a lot less opinionated than GNOME devs. If they could, GNOME devs would question the use case of your clothes, conclude they’re useless and then strip you naked. KDE devs will be fine with whatever you’re wearing.
Now as you may have gathered I definitely prefer one over the other, but I do recognize some people may like GNOME for its simplicity, looks, flow and I even heard some like the lack of customization because it prevents them from getting distracted with tinkering. All in all use case depends on what you want to do with it, tho hopefully Cosmic DE beats the shit outta GNOME devs those damn pricks.