Their respective head gear reveals their characters. Argyus is the leader of the senate commandos, but he's betrayed the Republic and is helping Nute Gunray escape. He seems more concerned with himself than either side of the war though, telling Gree that he wanted "a life with more than empty servitude" and gloating to Gunray after a successful escape that "I'll be a legend for this." His shifting loyalty is represented by his retaining his helmet, which obscures his face:
Gree, on the other hand, is steadfastly loyal to the Republic. When Gunray tries to bribe him at the beginning of the episode (saying "I am a man of great wealth, and I can be very generous to my allies"), he doesn't even consider it, and he's indignant about Argyus' betraying the Republic. There's no deception with Gree, which is represented by his not wearing a helmet here. He's not hiding anything.
As far as their positions, Argyus and Gree are parallel characters. Argyus is a captain, and Gree is a commander. By the end of this episode, their character arcs reveal the value of their choices. Gree has a virtuous morality and survives the incident, but Argyus, who seems concerned with only his own interests, is killed by Ventress:
