The Inkosi drop point and the Zaan harpooned style blades both have the same thickness, therefore both are more stout than the 21's blade. In fact I had read on the CRK's subforum somewhere that the Inkosi's tip was stronger than the Zaan's! But I get your point about the Zaan's blade shape with that swedge which makes is "sexier" looking to some including yours truly
Tony is also correct about the way the different way the stud is positioned. Although you may get away with a righty Inkosi (which is dual thumb studded), you may get very frustrated with a righty Zaan.