How much does armor affect damage reduction?

So I recently did an experiment to find the effect of armor points (same armor type) on damage reduction. (You can try yourself)

To start I entered the "Punic Wars" conquest as Turdetani (allied to Carthage on the Iberian Peninsula)

On the top part of the map I found 2 units that both had LIGHT ARMOR, but different armor points:
Light infantry 8 armor points
Light cavalry 12 armor points

I then moved the light infantry to Lusitani territory, declared war on them and attacked a unit of theirs. I did this 3 times and received around 130 dmg on avg

Then I restarted the conquest and attacked the same Lusitanian unit with the light cavalry after declaring war on them. On avg I also received around 128 dmg.

So I concluded that armor points don't affect damage reduction that significantly, only armor type does. This means that upgrading armor on any of your units (through the senate) useless.