WARNING: I do not have, and have never used, a Carlson data collector.
But from what I've been told, the Carlson data collectors let the field guy create all the linework in the field. You can then dump this data into C3D, but unfortunately (again, from what I've been told), it all basically comes in as a bunch of linework and symbols all on one layer. So, from what I've been told, people might use this feature once or twice, but then it becomes a "novelty", and they go back to generating the linework in CAD. The linework generated in the data collector is still useful for helping the field guy stay oriented and keep track of what still needs to be shot, but other than that, it is not used.
That's just what I've been told - someone who actually uses Carlson data collectors might chime in with something else.