They do different things - look for the balance you like. Command stars if you want a general to lead your armies, feathers (acumen) to improve income throughout your realm, piety to improve the piety of your generals and the zeal of your provinces, dread (and influence once you become king) to improve loyalty. The stats of your king will be reflected in the stats of your generals and of new units you create - better kings beget better generals. Loyalty is often pretty low right after a succession, but you can get it up pretty quickly if you don't have any disasters right away.