system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] What is the durability of Iron Man's suits?

The durability of the suits seems to vary so greatly. IIRC, his Mark 3 suit was able to withstand: 
1. A direct tank shot

2. Punch through the wing
 of an F-22 without suffering much damage

In Iron Man 2, his portable suit takes some damage but does okay against Whiplash. 

In The Avengers, his Mark VI suit suffers a decent amount of damage when pushed through the fan, but is able to tank some damage from Thor as well (though Thor is clearly stronger and causes more damage then he receives). His Mark VII armor is able to withstand the Battle of New York, up until the whole pushing a nuke through a portal thing.

Now Iron Man 3 is where it gets iffy. A lot of the Iron Legion suits seem super weak. Now, yes, extremis powered people are clearly strong, but at the same time, it is clear that the Iron Man 3 suits are weaker than even his earlier designs. 

In the Age of Ultron we're back to 'strong' Iron man for the most part, including the entertaining Hulkbuster fight that Iron Man manages to outlast the Hulk in. 

Now, in Civil War, we go back to 'weak' Iron Man. The Iron Man from the first two movies or the Avengers would not get ravaged by Bucky and Cap, even knowing how good they are at close range combat. 

So, what is the ultimate consensus on how durable his suits are? (or is it merely a question of as required by plot)
gpt
The Iron Legion suits were basically all prototypes, created during sleep-deprived nights when Tony was trying to get through his PTSD by obsessively inventing new suits.  It's no surprise that they were comparatively fragile, because they'd gone through none of the testing and optimization of an actual field-ready suit.  Each of them was basically a demonstration or proof of concept of a certain idea or innovation.  

Regarding Civil War, the suit Stark was using against Cap and Bucky came from his helicopter, ie it was also a suit designed for portability and weight efficiency, instead of providing the best durability or power.  Furthermore, recall that Stark spent a lot of that battle fighting on Cap and Bucky's home turf, that is to say, in close-range hand-to-hand combat.  Cap and Bucky are two of the strongest and most skillful pugilists the world has ever seen, and even Friday acknowledges that Stark is completely outmatched in hand to hand combat against Cap.