I've heard they use psychedelic drugs to get us the best drivers possible. With "they" I mean the bug hunters over at AMD.
XFCE... nice, but the development is too slow. Great KDE4 and that bad Gnome do not need much more RAM etc. and offer many more features while having a faster development process.
The features are quite different. I haven't counted them so I don't know who is ahead. But I do love the ability to minimize apps on your desktop background. Just get a ton of RAM and always have your files and stuff open...