At later points in the game you can -easily- cap Armor with everything that has a blacksmithing perk. When you are looking at late game (as early as level 20) figures, armor is irrelevant, because you are hitting the armor cap. Period.

Dismissing the fact that heavy armor is better at each tier by a not-insignificant margin is a disservice to optimization.

Early game, your choice of armor (Light, Heavy, Cloth with Alteration Spells, whatever) is important. By mid to late game, it's irrelevant.