Rereading Caesar's "I could be well moved, if I were as you" speech now, it sounds a lot like he's "the decider" ― i.e. constancy is held as a virtue in and of itself, even should the metaphor point toward massive narcissism: how many Caesars does it take to screw in a light bulb?
The world revolves around him.
And as it turns out (et tu, Brute?), he was right. He had "no fellow." The end result of egotism is isolation.
Brutus, on the other hand, in his "our cause is ripe" speech, sees the world as a place of interconnected flux, where forces move that are much bigger than us, and we must catch the tide accordingly. He's the liberal, maybe, to Caesar's W. Or at least the Colin Powell. He reflects the world around him, and is perhaps ultimately presented as too reflective in a number of senses. When Cassius offers to be his "glass" and reminds Brutus that "the eye sees not itself/but by some other thing," he is tapping into Brutus as a creature of context. What Brutus perhaps forgets is the paradox embedded in the metaphor: on the one hand, the mirror never lies, while on the other, that's all it can do ― offering a two-dimensional world of complete reversals where left is right, and right is wrong.
I'd be tempted to put the two side-by-side for my students and consider how they intereact in terms of nautical navigation. The constellations and Caesar's Pole star constancy would be necessary to find one's way, yet knowledge of the currents and tides would be equally beneficial, perhaps.
They Say He Made A Good End
13 hours ago