Question:

Should I create a terrain model from corridor mesh elements or 3D features?

Answer:

It is acceptable to use either the linear features or the corridor mesh when creating a terrain model from a corridor. Either method will produce a terrain model that is ruled to the corridor and will update as changes are made to the corridor. The advantage to using 3D features is that if you intend to push the terrain model out to a native format (such as a DTM), the features will be available.