armor advantage incongruency

[iosys2]

If a division has higher armor than the enemy got 1/2x damage and do 2x damage

But suppose I invest in enhance armor for my ARM but not (yet) in enhanced gun and suppose the enemy does the same

I will have ARM with AC 10 and AP 7

So what happen if 2 of such ARMs fight each other? Both will have Armor advantage!?!?

I.e. my AC is higher his AP so I do 2x damage but his AC is higher of my AP so he gets 1/2x
At the end we both got 2 * 1/2 = 1 x damage?

So armor advantage is de facto null?

 

[Big Nev]

I think your assessment is correct.
If neither side can penetrate the other, status quo is restored.
Why is this incongruent?