No significant difference. And I should note – Gnome and KDE are desktop environments, not window managers. Window managers sidestep the issue of UI integration, etc. in the first place, because they aren't bundled with other software.
As you said, if you care for UI integration, I always look at the applications when deciding which one to use. (I switch quite frequently.) In all honesty, I currently use KDE because I feels that its file browser and text editor, Dolphin and KWrite, are more powerful than their Gnome counterparts, Nautilus and gedit.
None of that really matters though, since both desktop environments now have support for emulating the other. Though in fact, I'm typing this in an unthemed, GTK-based Firefox. So, my answer is no, Gnome and KDE are not worlds apart in terms of functionality.
Two years ago, I would have said Gnome prefers simplicity while KDE prefers customizability. But KDE 4 changed things greatly. KDE is now a little flashier than Gnome, but beyond that, they're essentially the same.
what you meant by "sidestepping the issue of UI Integration"? – Geek – 2013-03-19T18:44:17.070