The desert nomads ride and hunt dinosaur herds on the former seabeds of Mars, living by a code of barbarian honor that reveres strength and cleverness, looks at magic with scorn, and distrusts the old ways. Desert nomads also distrust ancient technology. They are kind of dinosaur-riding Mongols/Cossacks/Dothraki/Hell's Angels — hard, superstitious, communal, and hierarchical. They live by a code no civilized person could really admire, they love their rides and their freedom, and they have a disdain for the ways of "proper" civilized folk.
The Canal City folk see themselves as the descendants of Ancient Mars, keepers of the ancient history and traditions of the Red Planet, and guardians of the great heritage of Mars. But they are decadent and fractious, caught up in politics, vendetta, honor killings, and upholding a dying noble class. They lack unity or vision, even as the Terrans look to plunder and colonize— mostly because they see their ancient ways as superior to Terrans. This despite the fact that they have forgotten the old technologies and fallen into a steep decline from their ancient days of glory. They value honor and propriety, prefer to track favor and fealty over nation and planet, and are more fond of drinking, dance, and dueling than of learning, discovery, and the common good.