Hi Marc!
A friend and I went on a Trip last week, both on XT660Z, he has the Tourance and I have the Sirac. We were driving through a forest mostly on sandy ground. His Tourance perform much better than my Siracs! I dropped my bike once in the sand, he had much less problems. As you said, its about Confidence. Of course knobbies are better, but as a compromise they are not bad. And if you drop, hey, its a (big) Dirt Bike. No Problem. When my Z was new I also never want to let it get dirty, but after a while...
Here some pics where I dropped it, when it was new and today...
JUST DO IT!!! The fun comes back instantly!