I'm sorry Aaron, but GStreamer doesn't handle DVD playback correctly. Xine does.
People used to say "Banshee doesn't support X/Y/Z. Rhythmbox does." And yet Banshee's architecture (and probably a few design decisions) have narrowed or closed that gap, and it's already starting to do things Rhythmbox can't.
GStreamer, as best I understand its internals, is about the same: a younger project than Xine, but a better architecture and more agile for new features/plugins.