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It's just personal preference. Gnome looks professional to me, nicely streamlined. KDE looks like a toy to me, some hideous, garish Fisher-Price toy.
But overall I like both KDE and Gnome. I agree with the other poster that the two camps should stop arguing and the apps should be interoperable so we all can enjoy the best of all worlds. Kudos to both the KDE and Gnome teams, you're both doing great. But arguing about the colours or grey-scale is like arguing about favorite foods. There is no wrong answer, just personal preferences.