They are both great knives in their place and IMO they hold different places, although they of course overlap.
The TK2 is a pretty standard European bushcrafter style knife. The slimmer blade with more acute point makes it great for bushcraft in temperate zones with hard woods. Tasks like drilling, notching, splitting, food prep etc are no bother. The preparing of some animals and wood types is where it would start to fall off though. Fine for fish, wood pidgen, rabbits and mushrooms, as well as nice hard woods like Chestnut, Oak, Sycamore, Lyme etc. For larger animals like dear, hogs or pelt beasts I would prefer to have a bit more belly and less guard.
The Nyala is a more utility style blade and can handle a large range of tasks comfortably and well. I have used one in Europe and in Asia with pleasing results, I have found my "Euro bushcrafters" don't seem to do so well in Asia. The woods in Asia tend to be hard and brittle... when sun baked dry

so that is where the taller blade and grind on the Nyala helps with breaking down those woods. The grind on the TK2 saves it there over a scandy or sabre grind but it's thin point and slim blade can see issues on hard brittle woods. The grinds are rather different but in performance the full flat convex Vs high hollow are actually pretty similar when all is said and done, IMO.
The blade profile and near totally neutral ergos are what put the Nyala on top for me, as well as its materials. I don't mind a synthetic sheath as in Asia leather rots realy quickly if you don't mollycoddle it. I carry my Nyala in kydex but I do like the standard leather sheath. The steel is good on both knives, but san-mai is not a particular selling point for me so I would not feel I'm losing anything by buying a single steel knife.
That may or may not mean anything to you and is purely based on my personal uses, but it's why I have chosen the Nyala now I live in Taiwan over the "Euro style" knives more similar to the TK2 I used to use back home.
