Ranked in these QuestionsQuestion Ranking
Pro Lightweight and desktop independent
Pro Great and beautiful theme support
It's very easy to create themes.
Pro Can choose to open windows at center of screen or edge
Pro Integrated compositing manager
XFWM has an integrated compositing manager, though it does have screen tearing.
Pro Left-half/Right-half window snapping
XFWM has a built-in option for window snapping.
Con Composite manager has screen tearing
The included composite manager in XFWM has screen tearing.
It should be mentioned that there's a workaround though:
compton --backend xrender --vsync opengl