I have both, but use the small sebenza MUCH more often. The Mnandi is plenty capable, but I ending up reaching for a sebenza more often. In the looks department, the Mnandi (IMO) looks more like an office knife with the wood covering both sides, the polished blade, and the sleek clip. The sebenza is available with inlays, but that would be more expensive.
In the end, you can't go wrong with either one. I know this sounds crazy, but if you can swing it get both and sell the one you like less on the exchange. You will take a minimal loss, but you will know you made the correct choice!