Lol I'm been trying to look up the same info. The lack of info prevents you from building an optimal armor set. You can't even pick between the two selectable perks aside from guessing. It doesn't appear to adjust the amount of armor within the subclass stats either. This is one among many hidden stats in this game that can limit your ability especially in pvp. Only think you can do is hope to find a youtuber that's ran tests to determine its usefulness. Why do this Bungie

You have more armor which means you can take a bit more damage before dying