It's funny how he said "best one for bossing" and you are all talking about which one is better for PKing...
For bossing I'd go with the CLS, has a high attack to hit through boss defence, an attack speed of 3.0 seconds I think, which isn't as slow as the maul, Because of its high attack in both stab and slash you can both use these to your advantage if the boss has a weakness to any of these, also it is one-handed so you can use it with another shield, or a dragon defender. If you pair it with a dragon defender its slash accuracy surpasses that of the godswords by 16 points. So I'd probably choose CLS.