Mark:
The hardest sort of ground is a moderately steep site that has a steady slope from one side to the other. Then, the only way to build holes is to bench them into the side of the hill, and it all gets very repetitive. If the site bottoms out and comes back up a bit on the far side, and there's not a protected stream or something in the bottom, then you've got a lot more opportunity to provide variety.
The other extreme is a dead flat site with a shallow water table.
Or, a site that's extensively cut up by environmentally sensitive areas.