A frame lock (Sebenza/Inkosi) is more secure than a slip joint (Impinda) if one were to hit it along the spine causing the knife to close on your hand. A frame lock needs to be unlocked to close, a slip joint just needs pressure applied to close. If cutting downwards both should be similarly durable/secure. Since the Inkosi blade is thicker than the Sebenza it is arguably a stronger blade as one exerts force downwards, but at the same time arguably slightly less slicey. I'm not sure what application you may be needing this knife for, but other than a very rare metallurgical defect one does not hear about any of these knives falling apart under any application. I have to believe the more slicey Sebenza blade edge may be more prone to dinging if hitting a nail or staple than an Inkosi because it is thinner along the edge. A Micarta inlay (resin infused canvas) is pretty darn indestructible and arguably provides a better grip, particularly in wet conditions. A knife slipping in hand is likely a much higher risk to cutting failure than the knife actually breaking. The Inkosi will serve you well.
