W-King D9

If you don't care that it floats and only need a speaker that is IPX6, then the W King D9 might be better, depending on your uses obviously. The main difference being that it has a 3.5mm Aux input which for whatever reason some people still want. It also has a memory card slot, if you want to simply put music on a small memory card and use the speakers controls to go through your playlist, and not have it tied to your phone. It is also slightly louder than the Motion Boom, although does sound anywhere near as good when directly compared.