With both types at 100 Heavy is an objectively better choice as the only difference mechanically at that point is how fast your armor is degrading….Light Armor.
Is light or heavy armor better in Oblivion? The best sword is found in Vindasel an Ayleid Ruin found on the south west side of Red Ring Road.Daedric and Glass are the best bases for your armor, although it is the enchantments that truly make your armor and weapons.