Well, I'm cocky enough to think I have enough skill to 'jib' off features along the trail 9/10 totally fine, 1/10 knees take the punishment. So in the interest of protecting my future riding I'll pad up.
Edit. Not XC as in race, local trails, plenty to keep you on your toes or knees...
I don't really know what that means but it almost certainly means I'd be walking where you'd be riding. I mostly need protection from stabby things because most of my MTBing is walking through things that aren't actually trails.. :D
What's the point of the knee guards for XC? What are they protecting against? Do you land on your knees often?