The Metzeler Karoo is pretty similar to the TKC 80s just a little better off-road and quicker wearing on-road. Since the goal of the 21/18 is off-road performance I went with the Metezlers but overall the difference is small. The Hideneau is not agressive enough in the open spaces between the blocks for me to feel safe when I'm asking a lot of the tire on the dirt. It makes a huge difference for me off-road. But they last a long time...
It was very interesting to me how the stability went up with the 18" rear when it gave the bike less rake but I ride pretty balanced and not over the back so maybe it let me relax more to still have the weight I want on the front?
I run Race Tech GS3 shocks front and rear, FYI. These are the best of the replacement shocks I have found. It is a big improvident over any others I have tried especially in the damping control available from the shock and they come valved and sprung correctly.