Essentially, each Unity only provides the mentioned unique RoEs, their own chat channel (some have so many members that you may rarely/never be able to join), and their own rank which will effect the potency of the Unity: effects on gear. I've yet to see any info on what benefits being in a low ranked Unity provide.

Quote Originally Posted by Zarchery View Post
Does anyone know if you have to be in the same Unity to, say, fight Wanted Notorious Monsters? Could 2 guys from Naja team up with 4 guys from Aldo and together fight Valkurm Imperator?
Correct. There's no limitations to this, anyone can participate as long as they have the RoE set and the required number of Accolades.