The “mobs” are different in that they will attack at a set and predictable time, when a horde might attack who knows when. Additionally, you can not go out into the field to attempt to clear out a mob, you must meet them as they attack the fort. Finally, they also present a threat to any projects that may be occurring in their path (such as reclaiming a square) because they force any one working in territory they enter to abandon the job.

Anyways looks like fun, I always enjoyed roughing it and travel but I never have the time nowadays lol.