My main character is a dual wield magicka templar. I have been spending the last few days trying to farm 2 sharpened spinner swords. I did manage to get two spinner swords with the defending trait and I started looking at the numbers. I currently run 5 light and 2 heavy. With 2 defending swords I get 5160 additional physical and spell resist plus I get to keep my other passives from my 5 pieces of light armor including the 5 piece passives, penetration and crit. Even if I went to all heavy armor I would only gain 5905 additional physical and spell resist over my current 5 light and 2 heavy and that is including the extra armor from the resolve passive.
And, most likely I would not do all heavy but 5 heavy and 2 light. In that case I come out way ahead mitigation wise using the two defending swords.
Now of course I would gain the additional benefits from the other heavy armor passives but all heavy really puts you into the close up melee play style which I am not. I prefer to use ranged attacks. I say all heavy puts you into a close up melee style because the two biggest benefits are the constitution and wrath passives which require you to be beat on.
Yes two sharpened swords gives 5160 penetration where the light armor passive only gives 4884 penetration but in my opinion the other passives of light armor make up for the slight lose in penetration.
So the whole point of this topic is to get people to start looking at many different builds to get the desired numbers you are looking for. Do not think you have to have heavy armor and sharpened weapons. Of course you can go to the extreme and be all heavy with defending weapons or all light with sharpened weapons but this is for the people that are trying to make well rounded builds. Try and make something work with the gear you end up with vs "I need to have that best in slot item."