I plan to use both swords and signs so light or medium - not interested in tanking, I'd rather try to use skill and parry/dodge a lot.
The definitive choice will depend on look. SInce it's only one point each, I might even take both Cat and Griffin school skills and equip whichever fit my current favorite armor.
Is it confirmed though that armor type doesn't affect your speed? I think I heard somewhere that it does affect something endurance-related. Like endurance regen, or the amount you lose when rolling.