This trail is not particularly exciting or technically difficult, it's just quite narrow at times, thus the Black rating. In the direction mapped here, you can coast to keep your pedals from hitting the edges, but the opposite direction might present a few challenges in places. It's commonly used by motocross riders, and therefore, substantially rutted in a number of sections at the time of writing. As mapped here, access to the start is also a challenge.
If given the choice of descending Buck Creek or Nottingham Ridge, I would choose Buck Creek unless I didn't want to finish in Avon. The hearty climber could make a loop climbing Davos Hill Climb to Nottingham Ridge (the opposite direction than mapped here), and connecting to Buck Creek.