Mounted on ponies, armored in scale and helmets, and equipped with the best of local goods, they are the heaviest cavalry in Britain, and this gives them a serious advantage over the cavalry light Britons.
The nobility of Caledonia are not so wealthy or well-equipped as their neighbors to the south, not to say that they are less well-off as the Celts of the continent. However, the Argyn Marca (Arg-en Mar-kah; "Noble Horse") are a far cry from the lower ranking levies that make up most of a Caledonian army. Mounted on ponies, armored in scale and helmets, and equipped with the best of local goods, they are the heaviest cavalry in Britain, and this gives them a serious advantage over the cavalry light Britons. Their charge is powerful, and their ponies are manueverable. Even against superior cavalry, their ability in forests can be used to great advantage. Their charge is augmented by an effective hail of javelins.
Historically, Caledonians hadn't many horses, resulting in most of their cavalry being composed of nobles and their retinues. Their horsemen were experienced fighting in the dense forests of northern Britain and in Ireland, and they were experienced at leading raids. Caledonians were not as disciplined as most of the enemies they faced, but they did have considerable ferocity and individual skill; augmented by their nobles, they could defeat seemingly superior enemies.