I just like the way XFCE4 runs "out of the box" so to speak. While there are a few things I would change with regard to the taskbar and panel I find the general setup more agreeable than a lot of the other desktop offerings available. It is also fairly easy to configure to my liking via its settings panel and comes with a decent set of themes. While these features may exist in other window managers/desktop environments XFCE4 seems to be one of the more convenient ways to get the features I require. I think with the plethora of WM/DEs available now there eventually becomes a point where, within a subgroup of similar WM/DEs, the choice of one over another is either based on extreme nitpicking or is simply made arbitrarily.