Considering the simplicity of the interface, Kaffeine could almost be a GNOME app. It opens on buttons for five basic functions -- playing a file, an audio CD, a video CD or DVD, and Digital TV, and a simplified version of the menus on the left side of the window. Things get more detailed when you actually select a function, but, on the whole, the interface is highly usable throughout.
Yet somehow, GNOME's Totem manages to be even simpler, providing basic playback features and an optional sidebar that displays details about the current selection. Totem's only real drawback is a screensaver that runs when audio files are playing, but that can be turned off in the preferences.
Brasero makes burning a CD or DVD as simple as Ubuntu makes installing an operating choice. Opening on a selection of five buttons, Brasero gives clear online instructions at every step of the way. However, despite the start of a plug-in library, options are more or less non-existent, so that if hardware compatibility or any other problems arise, you can do nothing to trouble to troubleshoot.
Rhythmbox is the default music player on GNOME, but is replaced by Banshee in Ubuntu. Both are oriented towards basic playback capability, although Banshee has a Context pane that can be opened from the View menu, and displays cover art. Next to Banshee, Rhythmbox feels like a no-frills app and has a text-heavy display that can be overwhelming to first-time users.
By contrast, KDE's Amarok reminds me of those studies by Victorians that attempted to be the last word on a subject. In a word, its feature list is exhaustive. If another music player comes out with a feature that Amarok lacks, then Amarok will have it by the next release. With apps for upcoming events, photos, lyrics, Wikpedia entries and more, Amarok gives the closest analog to linear notes that is possible online. It also contains advanced tools for generating automatic playlists, and dozens of plug-ins.
The largest drawback to Amarok is that it has trouble adding new tracks, especially once your collection rises above 5,000. New tracks are not always detected, and the total number of tracks may cease to change. These are problems from which neither Rhythmbox nor Banshee suffer. Both GNOME music players also seem to handle large number of tracks more quickly than Amarok.
Increasingly, the apps for each desktop show a distinct difference in design philosophy. These days, the typical GNOME app is usable at a glance, but limited to the most common functions. By contrast, the average KDE app is less user-friendly, but as complete as the imagination of its developers can make it, often supporting a wide array of plug-ins. Where a GNOME app often looks minimalist and highly organized, a KDE app often seems cluttered and unnecessarily complex -- at least at first glance.
There's something to be said for both design philosophies. But, fortunately, you don't have to choose. Although some users prefer to use only the native apps for their desktops, both GNOME and KDE ran each other's perfectly well, aside from a lag in startup time.
That means that you can run the app that best suits your purpose, and not worry about which desktop it was designed for. For example, if you just want to burn a DVD on standard hardware, you can use Brassero rather than K3B. But, if you run into trouble, then K3B might have the features to do a successful burn when Brassero can't. Nor are there any lack of alternatives, both desktop-specific and non-specific, for many software categories.
Chances are, though, that your mindset and work habits may lead you to prefer one application's ecosystem over another. If you're like me, you may even find that your preference sometimes varies with your mood. Or perhaps one desktop routinely includes an app that has no close comparison on the other, like GNOME's Cheese for cameras or KDE's Konversation for IRC.
Whatever your criteria, spend some time with all the alternatives, and you should soon learn which desktop's applications you prefer.